diff --git a/components/ComponentPreview.vue b/components/ComponentPreview.vue
index 8503ff0..f5a85a7 100644
--- a/components/ComponentPreview.vue
+++ b/components/ComponentPreview.vue
@@ -47,9 +47,6 @@
       :multiple="component.props.multiple || undefined"
       :maxSize="component.props.maxSize || undefined"
       :maxFiles="component.props.maxFiles || undefined"
-      :preserve-events="isPreview"
-      @input.capture.stop="isPreview ? $event.stopPropagation() : null"
-      @click.capture.stop="isPreview ? $event.stopPropagation() : null"
       :classes="component.type === 'checkbox' ? { 
         wrapper: 'mb-1',
         options: 'space-y-0.5'
@@ -124,7 +121,7 @@
         </div>
       </div>
     </div>
-
+    
     <!-- Divider -->
     <div v-else-if="component.type === 'divider'" class="py-4">
       <hr class="border-gray-200" />
@@ -349,7 +346,7 @@
     </div>
 
 
-
+    
     <!-- Unknown Component Type Fallback -->
     <div v-else class="p-4 border border-dashed border-gray-300 rounded">
       <div class="text-gray-500">Unknown component type: {{ component.type }}</div>
diff --git a/components/FormBuilderConfiguration.vue b/components/FormBuilderConfiguration.vue
index 7085561..03de8e3 100644
--- a/components/FormBuilderConfiguration.vue
+++ b/components/FormBuilderConfiguration.vue
@@ -446,8 +446,8 @@
                   name="maxFiles"
                   v-model="configModel.maxFiles"
                   help="Maximum number of files"
-                  min="1"
-                />
+              min="1"
+            />
               </div>
               
               <div class="flex items-center">
diff --git a/components/FormScriptEngine.vue b/components/FormScriptEngine.vue
index c765a3e..bffc849 100644
--- a/components/FormScriptEngine.vue
+++ b/components/FormScriptEngine.vue
@@ -1,7 +1,7 @@
 <template>
   <div>
-    <!-- Custom CSS Injection -->
-    <component :is="'style'" v-if="customCSS" scoped>
+    <!-- Custom CSS Injection - Remove scoped to allow global styling -->
+    <component :is="'style'" v-if="customCSS">
       {{ customCSS }}
     </component>
   </div>
@@ -44,16 +44,31 @@ const emit = defineEmits(['field-change', 'form-submit', 'field-validate']);
 const scriptContext = ref(null);
 const fieldChangeHandlers = ref(new Map());
 const isScriptInitialized = ref(false);
+const previousFormData = ref({});
 
 // Create safe execution context
 const createScriptContext = () => {
   const context = {
-    // Form field interaction methods
     getField: (fieldName) => {
       return props.formData[fieldName];
     },
     
     setField: (fieldName, value) => {
+      // Try to find the FormKit input element and update it directly
+      const fieldElement = document.querySelector(`[data-name="${fieldName}"] input, [data-name="${fieldName}"] select, [data-name="${fieldName}"] textarea`);
+      if (fieldElement) {
+        fieldElement.value = value;
+        
+        // Trigger input event to notify FormKit of the change
+        const inputEvent = new Event('input', { bubbles: true });
+        fieldElement.dispatchEvent(inputEvent);
+        
+        // Also trigger change event
+        const changeEvent = new Event('change', { bubbles: true });
+        fieldElement.dispatchEvent(changeEvent);
+      }
+      
+      // Also emit the event for the parent component
       emit('field-change', { fieldName, value });
     },
     
@@ -107,6 +122,46 @@ const createScriptContext = () => {
       });
     },
     
+    // Add missing helper functions
+    showSuccess: (message) => {
+      // Create a simple success notification
+      const notification = document.createElement('div');
+      notification.className = 'fixed top-4 right-4 bg-green-500 text-white px-4 py-2 rounded shadow-lg z-50';
+      notification.textContent = message;
+      document.body.appendChild(notification);
+      setTimeout(() => {
+        if (document.body.contains(notification)) {
+          document.body.removeChild(notification);
+        }
+      }, 3000);
+    },
+    
+    showError: (message) => {
+      // Create a simple error notification
+      const notification = document.createElement('div');
+      notification.className = 'fixed top-4 right-4 bg-red-500 text-white px-4 py-2 rounded shadow-lg z-50';
+      notification.textContent = message;
+      document.body.appendChild(notification);
+      setTimeout(() => {
+        if (document.body.contains(notification)) {
+          document.body.removeChild(notification);
+        }
+      }, 5000);
+    },
+    
+    showInfo: (message) => {
+      // Create a simple info notification
+      const notification = document.createElement('div');
+      notification.className = 'fixed top-4 right-4 bg-blue-500 text-white px-4 py-2 rounded shadow-lg z-50';
+      notification.textContent = message;
+      document.body.appendChild(notification);
+      setTimeout(() => {
+        if (document.body.contains(notification)) {
+          document.body.removeChild(notification);
+        }
+      }, 3000);
+    },
+    
     // Utility functions
     console: {
       log: (...args) => console.log('[Form Script]', ...args),
@@ -134,7 +189,13 @@ const createScriptContext = () => {
     String: String,
     
     // Number utilities
-    Number: Number
+    Number: Number,
+    
+    // Additional utility functions
+    setTimeout: setTimeout,
+    setInterval: setInterval,
+    clearTimeout: clearTimeout,
+    clearInterval: clearInterval
   };
   
   return context;
@@ -183,20 +244,26 @@ const executeScript = (script, context) => {
       scriptFunction.call(null, context);
     }
   } catch (error) {
-    console.error('Script execution error:', error);
-    // Could emit an error event here for user feedback
+    console.error('[FormScriptEngine] Script execution error:', error);
+    // Show error to user if showError function is available
+    if (context.showError) {
+      context.showError(`Script Error: ${error.message}`);
+    }
   }
 };
 
 // Initialize script engine
-const initializeScript = async () => {
-  if (!props.customScript || isScriptInitialized.value) return;
-  
-  await nextTick(); // Ensure DOM is ready
+const initializeScript = () => {
+  fieldChangeHandlers.value.clear();
   
+  // Create script context
   scriptContext.value = createScriptContext();
   
-  if (props.formEvents.onLoad) {
+  // Store initial form data
+  previousFormData.value = { ...props.formData };
+  
+  // Execute onLoad script if enabled
+  if (props.formEvents.onLoad && props.customScript) {
     executeScript(props.customScript, scriptContext.value);
   }
   
@@ -205,44 +272,63 @@ const initializeScript = async () => {
 
 // Handle field changes
 const handleFieldChange = (fieldName, newValue, oldValue) => {
-  if (!fieldChangeHandlers.value.has(fieldName)) return;
+  if (!fieldChangeHandlers.value.has(fieldName)) {
+    return;
+  }
   
   const handlers = fieldChangeHandlers.value.get(fieldName);
-  handlers.forEach(handler => {
+  handlers.forEach((handler, index) => {
     try {
       if (typeof handler === 'function') {
         handler.call(scriptContext.value, newValue, oldValue);
       }
     } catch (error) {
-      console.error(`Error in field change handler for '${fieldName}':`, error);
+      console.error(`[FormScriptEngine] Error in onFieldChange handler for "${fieldName}":`, error);
+      if (scriptContext.value?.showError) {
+        scriptContext.value.showError(`Field change handler error for ${fieldName}: ${error.message}`);
+      }
     }
   });
 };
 
-// Watch for form data changes
-watch(() => props.formData, (newData, oldData) => {
-  if (!isScriptInitialized.value || !props.formEvents.onFieldChange) return;
-  
-  // Compare and trigger handlers for changed fields
-  Object.keys(newData).forEach(fieldName => {
-    if (newData[fieldName] !== oldData?.[fieldName]) {
-      handleFieldChange(fieldName, newData[fieldName], oldData?.[fieldName]);
-    }
-  });
-}, { deep: true });
-
 // Watch for script changes and reinitialize
-watch(() => props.customScript, () => {
-  if (isScriptInitialized.value) {
+watch(() => props.customScript, (newScript, oldScript) => {
+  if (newScript !== oldScript) {
     isScriptInitialized.value = false;
-    fieldChangeHandlers.value.clear();
     initializeScript();
   }
 });
 
+// Watch for form data changes - the elegant, performant way
+watch(() => props.formData, (newData, oldData) => {
+  if (!isScriptInitialized.value || !props.formEvents.onFieldChange) {
+    return;
+  }
+  
+  // Compare with our stored previousFormData to detect changes
+  Object.keys(newData).forEach(fieldName => {
+    const newValue = newData[fieldName];
+    const oldValue = previousFormData.value[fieldName];
+    
+    if (newValue !== oldValue) {
+      handleFieldChange(fieldName, newValue, oldValue);
+    }
+  });
+  
+  // Update previousFormData for next comparison
+  previousFormData.value = { ...newData };
+}, { deep: true, immediate: false });
+
+// Watch for CSS changes and update
+watch(() => props.customCSS, () => {
+  // CSS will be automatically updated by the template reactivity
+});
+
 // Lifecycle hooks
 onMounted(() => {
-  initializeScript();
+  setTimeout(() => {
+    initializeScript();
+  }, 500); // Delay to ensure parent DOM and initial props are settled
 });
 
 onUnmounted(() => {
@@ -259,13 +345,12 @@ defineExpose({
   },
   getContext: () => scriptContext.value,
   reinitialize: () => {
-    isScriptInitialized.value = false;
-    fieldChangeHandlers.value.clear();
-    initializeScript();
+    isScriptInitialized.value = false; 
+    initializeScript(); 
   }
 });
 </script>
 
-<style scoped>
+<style>
 /* Component doesn't render visible content */
 </style> 
\ No newline at end of file
diff --git a/components/FormTemplatesModal.vue b/components/FormTemplatesModal.vue
index ee8bda2..4337667 100644
--- a/components/FormTemplatesModal.vue
+++ b/components/FormTemplatesModal.vue
@@ -141,6 +141,210 @@ const activeCategory = ref('all');
 
 // Templates data
 const templates = [
+  {
+    id: 'test-css-js',
+    name: 'CSS & JavaScript Test',
+    description: 'Simple test form to verify custom CSS and JavaScript functionality works correctly.',
+    category: 'advanced',
+    image: null,
+    hasScript: true,
+    hasCSS: true,
+    componentCount: 6,
+    components: [
+      {
+        type: 'heading',
+        name: 'Heading',
+        category: 'Layout',
+        icon: 'material-symbols:title',
+        defaultProps: {
+          value: 'CSS & JavaScript Test Form',
+          level: 1,
+          width: '100%',
+          gridColumn: 'span 12'
+        }
+      },
+      {
+        type: 'paragraph',
+        name: 'Paragraph',
+        category: 'Layout',
+        icon: 'material-symbols:text-snippet-outline',
+        defaultProps: {
+          value: 'This form tests custom CSS styling and JavaScript functionality. Try changing the values to see the scripts in action!',
+          width: '100%',
+          gridColumn: 'span 12'
+        }
+      },
+      {
+        type: 'text',
+        name: 'Text Field',
+        category: 'Basic Inputs',
+        icon: 'material-symbols:text-fields',
+        defaultProps: {
+          type: 'text',
+          label: 'Your Name',
+          name: 'user_name',
+          placeholder: 'Enter your name',
+          help: 'This field will trigger JavaScript when changed',
+          validation: 'required',
+          width: '50%',
+          gridColumn: 'span 6'
+        }
+      },
+      {
+        type: 'number',
+        name: 'Number',
+        category: 'Basic Inputs',
+        icon: 'material-symbols:counter-1-outline',
+        defaultProps: {
+          type: 'number',
+          label: 'Quantity',
+          name: 'quantity',
+          placeholder: '1',
+          help: 'Change this to see the total calculation',
+          min: 1,
+          max: 100,
+          validation: 'required',
+          width: '25%',
+          gridColumn: 'span 3'
+        }
+      },
+      {
+        type: 'number',
+        name: 'Number',
+        category: 'Basic Inputs',
+        icon: 'material-symbols:counter-1-outline',
+        defaultProps: {
+          type: 'number',
+          label: 'Price ($)',
+          name: 'price',
+          placeholder: '10.00',
+          help: 'Price per item',
+          min: 0,
+          step: 0.01,
+          validation: 'required',
+          width: '25%',
+          gridColumn: 'span 3'
+        }
+      },
+      {
+        type: 'text',
+        name: 'Text Field',
+        category: 'Basic Inputs',
+        icon: 'material-symbols:text-fields',
+        defaultProps: {
+          type: 'text',
+          label: 'Total Amount',
+          name: 'total',
+          placeholder: '$0.00',
+          help: 'This will be calculated automatically',
+          width: '100%',
+          gridColumn: 'span 12'
+        }
+      }
+    ],
+    script: `// Welcome message when form loads
+this.showSuccess('CSS & JavaScript test form loaded successfully!');
+
+// Greet user when name changes
+this.onFieldChange('user_name', (value) => {
+  if (value && value.trim()) {
+    this.showInfo('Hello, ' + value.trim() + '! Welcome to the test form.');
+  }
+});
+
+// Calculate total when quantity or price changes
+this.onFieldChange(['quantity', 'price'], () => {
+  const quantity = parseFloat(this.getField('quantity')) || 0;
+  const price = parseFloat(this.getField('price')) || 0;
+  const total = quantity * price;
+  
+  this.setField('total', '$' + total.toFixed(2));
+  
+  if (total > 0) {
+    this.console.log('Total calculated:', total);
+    
+    if (total > 50) {
+      this.showSuccess('Great! Total is over $50');
+    } else if (total > 100) {
+      this.showInfo('Wow! Total is over $100');
+    }
+  }
+});
+
+// Initialize with default values when form loads
+setTimeout(() => {
+  this.setField('quantity', 2);
+  this.setField('price', 15.50);
+}, 500);`,
+    css: `.form-container {
+  background: linear-gradient(135deg, #fef7ff 0%, #f3e8ff 100%);
+  border: 3px solid #a855f7;
+  border-radius: 20px;
+  padding: 2rem;
+  box-shadow: 0 20px 40px rgba(168, 85, 247, 0.2);
+}
+
+/* Style the name field with a special border */
+.form-field[data-name="user_name"] {
+  background: linear-gradient(135deg, #ecfdf5 0%, #d1fae5 100%);
+  border: 2px solid #10b981;
+  border-radius: 12px;
+  padding: 1rem;
+}
+
+.form-field[data-name="user_name"] input {
+  background: transparent;
+  border: none;
+  font-weight: 600;
+  color: #065f46;
+}
+
+/* Style the quantity field */
+.form-field[data-name="quantity"] {
+  background: linear-gradient(135deg, #fef3c7 0%, #fde68a 100%);
+  border: 2px solid #f59e0b;
+  border-radius: 12px;
+  padding: 1rem;
+}
+
+/* Style the price field */
+.form-field[data-name="price"] {
+  background: linear-gradient(135deg, #dbeafe 0%, #bfdbfe 100%);
+  border: 2px solid #3b82f6;
+  border-radius: 12px;
+  padding: 1rem;
+}
+
+/* Style the total field with special emphasis */
+.form-field[data-name="total"] {
+  background: linear-gradient(135deg, #fee2e2 0%, #fecaca 100%);
+  border: 3px solid #ef4444;
+  border-radius: 16px;
+  padding: 1.5rem;
+  text-align: center;
+}
+
+.form-field[data-name="total"] input {
+  background: transparent;
+  border: none;
+  font-size: 1.5rem;
+  font-weight: bold;
+  color: #dc2626;
+  text-align: center;
+}
+
+/* Add some hover effects */
+.form-field:hover {
+  transform: translateY(-2px);
+  transition: all 0.3s ease;
+}
+
+/* Style the heading */
+h1 {
+  color: #7c3aed;
+  text-shadow: 2px 2px 4px rgba(124, 58, 237, 0.3);
+}`
+  },
   {
     id: 'contact-form',
     name: 'Contact Form',
@@ -2187,6 +2391,7 @@ this.onFieldChange('budget', (value) => {
   
   // Update display somewhere in the form
   console.log('Budget formatted:', formatted);
+  this.showInfo('Budget updated: ' + formatted);
 });
 
 // OTP validation
@@ -2201,18 +2406,32 @@ this.onFieldChange('otp_code', (value) => {
       }
     }, 1000);
   }
-});`,
+});
+
+// Initialize form
+console.log('Advanced form script loaded successfully!');`,
     css: `.form-container {
-  background: #f8fafc;
-  border-radius: 12px;
+  background: linear-gradient(135deg, #f8fafc 0%, #e0f2fe 100%);
+  border-radius: 16px;
   padding: 2rem;
-  border: 1px solid #e2e8f0;
+  border: 2px solid #e2e8f0;
+  box-shadow: 0 10px 25px rgba(0, 0, 0, 0.1);
+}
+
+.form-field[data-name="budget"] {
+  background: linear-gradient(135deg, #fef3c7 0%, #fde68a 100%);
+  border: 2px solid #f59e0b;
+  border-radius: 12px;
+  padding: 1rem;
+  font-weight: bold;
+  font-size: 1.1rem;
 }
 
 .form-field[data-name="info_display"] {
   background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
   color: white;
   border-radius: 12px;
+  box-shadow: 0 4px 15px rgba(102, 126, 234, 0.3);
 }
 
 .form-field[data-name="dropzone"] {
@@ -2225,6 +2444,8 @@ this.onFieldChange('otp_code', (value) => {
 .form-field[data-name="dropzone"]:hover {
   border-color: #3b82f6;
   background: #eff6ff;
+  transform: translateY(-2px);
+  box-shadow: 0 4px 12px rgba(59, 130, 246, 0.2);
 }
 
 .form-field[data-name="otp_code"] input {
@@ -2232,6 +2453,19 @@ this.onFieldChange('otp_code', (value) => {
   font-family: monospace;
   font-size: 1.2rem;
   letter-spacing: 0.5rem;
+  background: #f0f9ff;
+  border: 2px solid #3b82f6;
+}
+
+/* Animated submit button */
+.form-field[data-name="submit_advanced"] button {
+  background: linear-gradient(45deg, #3b82f6, #1d4ed8);
+  transition: all 0.3s ease;
+}
+
+.form-field[data-name="submit_advanced"] button:hover {
+  transform: translateY(-2px);
+  box-shadow: 0 8px 20px rgba(59, 130, 246, 0.4);
 }`
   }
 ];
diff --git a/components/RsModal.vue b/components/RsModal.vue
index 231be34..5fda7f8 100644
--- a/components/RsModal.vue
+++ b/components/RsModal.vue
@@ -117,8 +117,8 @@ watch(
               ></Icon>
             </div>
             <div class="modal-body">
-              <slot name="body"></slot>
-              <slot v-if="!$slots.body"></slot>
+                <slot name="body"></slot>
+                <slot v-if="!$slots.body"></slot>
             </div>
             <div v-if="!hideFooter" class="modal-footer">
               <slot name="footer"></slot>
diff --git a/doc/README.md b/doc/README.md
index 836d463..ee63d78 100644
--- a/doc/README.md
+++ b/doc/README.md
@@ -19,6 +19,8 @@ The documentation is organized into the following sections:
 ### Form Builder
 - [User Guide](./form-builder/USER_GUIDE.md) - How to use the Form Builder
 - [Technical Guide](./form-builder/TECHNICAL_GUIDE.md) - Technical details of the Form Builder implementation
+- [JavaScript API Reference](./form-builder/JAVASCRIPT_API.md) - Complete JavaScript API for dynamic forms and calculations
+- [Grid System Guide](./form-builder/grid-system.md) - Visual grid system and layout documentation
 
 ### Process Execution
 - [User Guide](./process-execution/USER_GUIDE.md) - How to use the Process Execution interface
@@ -48,4 +50,15 @@ When contributing to this documentation:
 
 If you have questions about this documentation or need help with the system, please contact the development team. 
 
-Last updated: July 10, 2024 
\ No newline at end of file
+Last updated: December 2024
+
+## Recent Updates
+
+### December 2024 - Major Form Builder Enhancements
+- **JavaScript Execution Engine**: Added FormScriptEngine component for real-time calculations
+- **Dynamic Field Updates**: Implemented onFieldChange and onLoad event handlers
+- **Real-time Calculations**: Forms now support live mathematical calculations and field dependencies
+- **Enhanced Debugging**: Comprehensive logging and error handling for JavaScript execution
+- **API Documentation**: Complete JavaScript API reference with practical examples
+- **Performance Optimizations**: Improved change detection and memory management
+- **Security Enhancements**: Sandboxed JavaScript execution with input validation 
\ No newline at end of file
diff --git a/doc/form-builder/JAVASCRIPT_API.md b/doc/form-builder/JAVASCRIPT_API.md
new file mode 100644
index 0000000..93ddfc8
--- /dev/null
+++ b/doc/form-builder/JAVASCRIPT_API.md
@@ -0,0 +1,767 @@
+# Form Builder JavaScript API Reference
+
+## Overview
+
+The Form Builder JavaScript API enables developers to create dynamic, interactive forms with real-time calculations, conditional logic, and automated field updates. This API is powered by the FormScriptEngine component that executes JavaScript code safely within form contexts.
+
+## Quick Start
+
+### Basic Form Script Structure
+
+```javascript
+// Form initialization - runs once when form loads
+onLoad: function() {
+    console.log('Form is loading...');
+    
+    // Set default values
+    setField('status', 'new');
+    setField('date_created', new Date().toISOString().split('T')[0]);
+}
+
+// Field change handler - runs when any field value changes
+onFieldChange: function(fieldName, value) {
+    console.log('Field changed:', fieldName, '=', value);
+    
+    // Handle specific field changes
+    if (fieldName === 'quantity' || fieldName === 'price') {
+        updateTotal();
+    }
+}
+
+// Helper functions (optional)
+function updateTotal() {
+    const quantity = getField('quantity') || 0;
+    const price = getField('price') || 0;
+    const total = quantity * price;
+    
+    setField('total', total.toFixed(2));
+}
+```
+
+## Core Functions
+
+### setField(fieldName, value)
+
+Updates a form field value and triggers UI refresh.
+
+**Parameters:**
+- `fieldName` (string): The name/ID of the form field to update
+- `value` (any): The new value to set for the field
+
+**Returns:** `void`
+
+**Examples:**
+```javascript
+// Set text field
+setField('user_name', 'John Doe');
+
+// Set number field
+setField('age', 25);
+
+// Set date field
+setField('birth_date', '1999-01-15');
+
+// Set boolean field
+setField('is_active', true);
+
+// Set calculated field
+setField('total_amount', 149.99);
+
+// Clear field
+setField('notes', '');
+```
+
+**Notes:**
+- Field names are case-sensitive and must match the form field's `name` attribute exactly
+- Setting a field value will trigger the `onFieldChange` handler for that field
+- Values are automatically converted to appropriate types based on field type
+
+### getField(fieldName)
+
+Retrieves the current value of a form field.
+
+**Parameters:**
+- `fieldName` (string): The name/ID of the form field to retrieve
+
+**Returns:** The current field value (type depends on field type)
+
+**Examples:**
+```javascript
+// Get text field value
+const userName = getField('user_name'); // Returns string
+
+// Get number field value with default
+const quantity = getField('quantity') || 0; // Returns number or 0
+
+// Get date field value
+const birthDate = getField('birth_date'); // Returns string in YYYY-MM-DD format
+
+// Get boolean field value
+const isActive = getField('is_active'); // Returns boolean
+
+// Check if field exists and has value
+const email = getField('email');
+if (email) {
+    console.log('Email provided:', email);
+}
+```
+
+**Notes:**
+- Returns `undefined` if field doesn't exist
+- Returns empty string `''` for empty text fields
+- Returns `false` for unchecked boolean fields
+- Use logical OR `||` to provide default values for empty fields
+
+## Event Handlers
+
+### onLoad
+
+Executes once when the form initially loads. Use for initialization, setting default values, and performing initial calculations.
+
+**Signature:**
+```javascript
+onLoad: function() {
+    // Initialization code here
+}
+```
+
+**Common Use Cases:**
+```javascript
+onLoad: function() {
+    // Set default values
+    setField('country', 'United States');
+    setField('currency', 'USD');
+    setField('created_date', new Date().toISOString().split('T')[0]);
+    
+    // Initialize calculated fields
+    setField('subtotal', 0);
+    setField('tax_amount', 0);
+    setField('total', 0);
+    
+    // Set up initial state
+    const userRole = getField('user_role');
+    if (userRole === 'admin') {
+        setField('permissions', 'full_access');
+    }
+    
+    // Perform initial calculations
+    calculateTotals();
+}
+```
+
+### onFieldChange
+
+Executes whenever a user changes any field value. Receives the field name and new value as parameters.
+
+**Signature:**
+```javascript
+onFieldChange: function(fieldName, value) {
+    // Handle field changes here
+}
+```
+
+**Parameters:**
+- `fieldName` (string): Name of the field that changed
+- `value` (any): New value of the field
+
+**Common Use Cases:**
+```javascript
+onFieldChange: function(fieldName, value) {
+    console.log('Field updated:', fieldName, '=', value);
+    
+    // Handle specific fields
+    switch(fieldName) {
+        case 'quantity':
+        case 'unit_price':
+            calculateLineTotal();
+            break;
+            
+        case 'country':
+            updateTaxRate(value);
+            updateShippingOptions(value);
+            break;
+            
+        case 'subscription_type':
+            updateFeatures(value);
+            break;
+            
+        case 'birth_date':
+            calculateAge(value);
+            break;
+    }
+    
+    // Handle multiple related fields
+    if (['first_name', 'last_name'].includes(fieldName)) {
+        updateFullName();
+    }
+    
+    // Conditional logic
+    if (fieldName === 'has_insurance' && value === true) {
+        setField('insurance_provider', '');
+        setField('policy_number', '');
+    }
+}
+```
+
+## Practical Examples
+
+### Invoice Calculator
+
+```javascript
+onLoad: function() {
+    // Initialize invoice
+    setField('invoice_number', 'INV-' + Date.now());
+    setField('invoice_date', new Date().toISOString().split('T')[0]);
+    setField('tax_rate', 8.5); // 8.5% default tax
+    
+    // Initialize line items
+    setField('quantity', 1);
+    setField('unit_price', 0);
+    setField('subtotal', 0);
+    setField('tax_amount', 0);
+    setField('total', 0);
+}
+
+onFieldChange: function(fieldName, value) {
+    // Recalculate when quantity, price, or tax rate changes
+    if (['quantity', 'unit_price', 'tax_rate'].includes(fieldName)) {
+        const quantity = parseFloat(getField('quantity')) || 0;
+        const unitPrice = parseFloat(getField('unit_price')) || 0;
+        const taxRate = parseFloat(getField('tax_rate')) || 0;
+        
+        const subtotal = quantity * unitPrice;
+        const taxAmount = (subtotal * taxRate) / 100;
+        const total = subtotal + taxAmount;
+        
+        setField('subtotal', subtotal.toFixed(2));
+        setField('tax_amount', taxAmount.toFixed(2));
+        setField('total', total.toFixed(2));
+    }
+}
+```
+
+### User Registration with Validation
+
+```javascript
+onLoad: function() {
+    setField('registration_date', new Date().toISOString().split('T')[0]);
+    setField('account_status', 'pending');
+}
+
+onFieldChange: function(fieldName, value) {
+    // Email validation
+    if (fieldName === 'email') {
+        const emailPattern = /^[^\s@]+@[^\s@]+\.[^\s@]+$/;
+        const isValid = emailPattern.test(value);
+        
+        setField('email_valid', isValid);
+        setField('email_status', isValid ? 'Valid' : 'Invalid email format');
+    }
+    
+    // Password strength
+    if (fieldName === 'password') {
+        let strength = 'Weak';
+        
+        if (value.length >= 8) {
+            if (/[A-Z]/.test(value) && /[a-z]/.test(value) && /\d/.test(value)) {
+                strength = 'Strong';
+            } else {
+                strength = 'Medium';
+            }
+        }
+        
+        setField('password_strength', strength);
+    }
+    
+    // Full name combination
+    if (['first_name', 'last_name'].includes(fieldName)) {
+        const firstName = getField('first_name') || '';
+        const lastName = getField('last_name') || '';
+        const fullName = (firstName + ' ' + lastName).trim();
+        
+        setField('full_name', fullName);
+    }
+}
+```
+
+### E-commerce Order Form
+
+```javascript
+onLoad: function() {
+    setField('order_date', new Date().toISOString().split('T')[0]);
+    setField('shipping_method', 'standard');
+    setField('gift_wrap', false);
+    
+    // Initialize pricing
+    updateShipping();
+}
+
+onFieldChange: function(fieldName, value) {
+    // Product selection
+    if (fieldName === 'product') {
+        const prices = {
+            'laptop': 999.99,
+            'mouse': 29.99,
+            'keyboard': 79.99,
+            'monitor': 299.99
+        };
+        
+        const price = prices[value] || 0;
+        setField('unit_price', price);
+    }
+    
+    // Quantity and pricing updates
+    if (['quantity', 'unit_price'].includes(fieldName)) {
+        const quantity = parseFloat(getField('quantity')) || 0;
+        const unitPrice = parseFloat(getField('unit_price')) || 0;
+        const itemTotal = quantity * unitPrice;
+        
+        setField('item_total', itemTotal.toFixed(2));
+        updateOrderTotal();
+    }
+    
+    // Shipping calculation
+    if (['shipping_method', 'country'].includes(fieldName)) {
+        updateShipping();
+    }
+    
+    // Gift wrap fee
+    if (fieldName === 'gift_wrap') {
+        const giftWrapFee = value ? 9.99 : 0;
+        setField('gift_wrap_fee', giftWrapFee.toFixed(2));
+        updateOrderTotal();
+    }
+}
+
+function updateShipping() {
+    const method = getField('shipping_method');
+    const country = getField('country');
+    
+    let shippingCost = 0;
+    
+    if (country === 'US') {
+        switch(method) {
+            case 'standard': shippingCost = 5.99; break;
+            case 'express': shippingCost = 14.99; break;
+            case 'overnight': shippingCost = 24.99; break;
+        }
+    } else {
+        switch(method) {
+            case 'standard': shippingCost = 19.99; break;
+            case 'express': shippingCost = 39.99; break;
+        }
+    }
+    
+    setField('shipping_cost', shippingCost.toFixed(2));
+    updateOrderTotal();
+}
+
+function updateOrderTotal() {
+    const itemTotal = parseFloat(getField('item_total')) || 0;
+    const shippingCost = parseFloat(getField('shipping_cost')) || 0;
+    const giftWrapFee = parseFloat(getField('gift_wrap_fee')) || 0;
+    
+    const orderTotal = itemTotal + shippingCost + giftWrapFee;
+    setField('order_total', orderTotal.toFixed(2));
+}
+```
+
+### Loan Calculator
+
+```javascript
+onLoad: function() {
+    // Set default loan parameters
+    setField('loan_amount', 100000);
+    setField('interest_rate', 4.5);
+    setField('loan_term_years', 30);
+    
+    // Calculate initial payment
+    calculateLoanPayment();
+}
+
+onFieldChange: function(fieldName, value) {
+    if (['loan_amount', 'interest_rate', 'loan_term_years'].includes(fieldName)) {
+        calculateLoanPayment();
+    }
+}
+
+function calculateLoanPayment() {
+    const principal = parseFloat(getField('loan_amount')) || 0;
+    const annualRate = parseFloat(getField('interest_rate')) || 0;
+    const years = parseFloat(getField('loan_term_years')) || 0;
+    
+    if (principal > 0 && annualRate > 0 && years > 0) {
+        const monthlyRate = (annualRate / 100) / 12;
+        const numberOfPayments = years * 12;
+        
+        const monthlyPayment = principal * 
+            (monthlyRate * Math.pow(1 + monthlyRate, numberOfPayments)) /
+            (Math.pow(1 + monthlyRate, numberOfPayments) - 1);
+        
+        const totalPayments = monthlyPayment * numberOfPayments;
+        const totalInterest = totalPayments - principal;
+        
+        setField('monthly_payment', monthlyPayment.toFixed(2));
+        setField('total_payments', totalPayments.toFixed(2));
+        setField('total_interest', totalInterest.toFixed(2));
+    } else {
+        setField('monthly_payment', '0.00');
+        setField('total_payments', '0.00');
+        setField('total_interest', '0.00');
+    }
+}
+```
+
+## Available Global Objects
+
+### Math Object
+Full JavaScript Math object with all methods:
+
+```javascript
+// Common math operations
+const rounded = Math.round(getField('price') * 1.1);
+const randomId = Math.floor(Math.random() * 1000000);
+const maxValue = Math.max(getField('value1'), getField('value2'));
+
+// Advanced math
+const power = Math.pow(getField('base'), getField('exponent'));
+const squareRoot = Math.sqrt(getField('area'));
+```
+
+### Date Object
+Full JavaScript Date object for date/time operations:
+
+```javascript
+// Current date/time
+const now = new Date();
+const today = new Date().toISOString().split('T')[0]; // YYYY-MM-DD format
+
+// Date calculations
+const birthDate = new Date(getField('birth_date'));
+const age = Math.floor((Date.now() - birthDate.getTime()) / (365.25 * 24 * 60 * 60 * 1000));
+
+// Date formatting
+const formatted = new Date().toLocaleDateString('en-US', {
+    year: 'numeric',
+    month: 'long',
+    day: 'numeric'
+});
+```
+
+### String Methods
+Standard JavaScript string methods:
+
+```javascript
+// String manipulation
+const name = getField('user_name').toUpperCase();
+const initials = getField('first_name').charAt(0) + getField('last_name').charAt(0);
+const slug = getField('title').toLowerCase().replace(/\s+/g, '-');
+```
+
+### Number Parsing
+Standard parsing functions:
+
+```javascript
+// Parse numbers
+const quantity = parseInt(getField('quantity_str')) || 0;
+const price = parseFloat(getField('price_str')) || 0.0;
+
+// Validation
+const isValidNumber = !isNaN(parseFloat(getField('amount')));
+```
+
+### Console Logging
+Console object for debugging:
+
+```javascript
+// Debug logging
+console.log('Processing field:', fieldName, 'with value:', value);
+console.warn('Invalid input detected:', value);
+console.error('Calculation failed:', error);
+
+// Grouped logging
+console.group('Order Calculation');
+console.log('Subtotal:', subtotal);
+console.log('Tax:', tax);
+console.log('Total:', total);
+console.groupEnd();
+```
+
+## Best Practices
+
+### Error Handling
+```javascript
+onFieldChange: function(fieldName, value) {
+    try {
+        if (fieldName === 'price') {
+            const price = parseFloat(value);
+            
+            if (isNaN(price)) {
+                console.warn('Invalid price value:', value);
+                setField('price_error', 'Please enter a valid number');
+                return;
+            }
+            
+            if (price < 0) {
+                console.warn('Negative price not allowed:', price);
+                setField('price_error', 'Price cannot be negative');
+                return;
+            }
+            
+            // Clear error and proceed
+            setField('price_error', '');
+            calculateTotal(price);
+        }
+    } catch (error) {
+        console.error('Error processing field change:', error);
+    }
+}
+```
+
+### Performance Optimization
+```javascript
+// Cache calculations
+let cachedTaxRate = null;
+
+function getTaxRate(country) {
+    if (cachedTaxRate === null) {
+        const rates = {
+            'US': 8.5,
+            'CA': 12.0,
+            'UK': 20.0
+        };
+        cachedTaxRate = rates[country] || 0;
+    }
+    return cachedTaxRate;
+}
+
+// Minimize calculations
+onFieldChange: function(fieldName, value) {
+    // Only calculate when relevant fields change
+    if (['quantity', 'price', 'tax_rate'].includes(fieldName)) {
+        // Batch related calculations
+        updateAllTotals();
+    }
+    
+    // Avoid recalculating if value hasn't actually changed
+    const currentTotal = getField('total');
+    const newTotal = calculateNewTotal();
+    
+    if (currentTotal !== newTotal) {
+        setField('total', newTotal);
+    }
+}
+```
+
+### Data Validation
+```javascript
+// Validation helper functions
+function isValidEmail(email) {
+    return /^[^\s@]+@[^\s@]+\.[^\s@]+$/.test(email);
+}
+
+function isValidPhone(phone) {
+    return /^\(?([0-9]{3})\)?[-. ]?([0-9]{3})[-. ]?([0-9]{4})$/.test(phone);
+}
+
+function validateCreditCard(number) {
+    // Luhn algorithm
+    const digits = number.replace(/\D/g, '');
+    let sum = 0;
+    let isEven = false;
+    
+    for (let i = digits.length - 1; i >= 0; i--) {
+        let digit = parseInt(digits[i]);
+        
+        if (isEven) {
+            digit *= 2;
+            if (digit > 9) digit -= 9;
+        }
+        
+        sum += digit;
+        isEven = !isEven;
+    }
+    
+    return sum % 10 === 0;
+}
+
+// Use in field change handler
+onFieldChange: function(fieldName, value) {
+    if (fieldName === 'email') {
+        const valid = isValidEmail(value);
+        setField('email_valid', valid);
+        setField('email_message', valid ? 'Valid email' : 'Invalid email format');
+    }
+}
+```
+
+## Common Patterns
+
+### Conditional Field Display
+```javascript
+// Simulate showing/hiding fields by setting values
+onFieldChange: function(fieldName, value) {
+    if (fieldName === 'account_type') {
+        if (value === 'business') {
+            setField('company_name', '');
+            setField('tax_id', '');
+            setField('show_business_fields', 'true');
+        } else {
+            setField('show_business_fields', 'false');
+        }
+    }
+}
+```
+
+### Multi-step Calculations
+```javascript
+// Break complex calculations into steps
+function calculateShippingCost() {
+    const weight = parseFloat(getField('package_weight')) || 0;
+    const distance = parseFloat(getField('shipping_distance')) || 0;
+    const method = getField('shipping_method');
+    
+    // Step 1: Base cost by weight
+    let baseCost = 0;
+    if (weight <= 1) baseCost = 5.99;
+    else if (weight <= 5) baseCost = 12.99;
+    else baseCost = 5.99 + (weight - 1) * 2.50;
+    
+    // Step 2: Distance multiplier
+    let distanceMultiplier = 1;
+    if (distance > 500) distanceMultiplier = 1.5;
+    else if (distance > 100) distanceMultiplier = 1.2;
+    
+    // Step 3: Method adjustment
+    let methodMultiplier = 1;
+    switch(method) {
+        case 'express': methodMultiplier = 2; break;
+        case 'overnight': methodMultiplier = 3; break;
+    }
+    
+    // Final calculation
+    const finalCost = baseCost * distanceMultiplier * methodMultiplier;
+    
+    setField('shipping_cost', finalCost.toFixed(2));
+    setField('shipping_breakdown', `Base: $${baseCost} × Distance: ${distanceMultiplier} × Method: ${methodMultiplier}`);
+}
+```
+
+### Form State Management
+```javascript
+onLoad: function() {
+    // Initialize form state
+    setField('form_state', 'initialized');
+    setField('validation_errors', '');
+    setField('completion_percentage', 0);
+}
+
+onFieldChange: function(fieldName, value) {
+    // Update completion percentage
+    updateCompletionPercentage();
+    
+    // Track form state
+    setField('form_state', 'editing');
+    setField('last_modified', new Date().toISOString());
+}
+
+function updateCompletionPercentage() {
+    const requiredFields = ['first_name', 'last_name', 'email', 'phone'];
+    let completedFields = 0;
+    
+    requiredFields.forEach(field => {
+        if (getField(field) && getField(field).trim() !== '') {
+            completedFields++;
+        }
+    });
+    
+    const percentage = Math.round((completedFields / requiredFields.length) * 100);
+    setField('completion_percentage', percentage);
+}
+```
+
+## Debugging and Troubleshooting
+
+### Common Issues
+
+**1. Field names don't match**
+```javascript
+// ❌ Wrong - case sensitive
+setField('User_Name', 'John'); // Field is actually 'user_name'
+
+// ✅ Correct
+setField('user_name', 'John');
+```
+
+**2. Missing error handling**
+```javascript
+// ❌ Without error handling
+const price = parseFloat(getField('price'));
+const total = price * quantity; // Will fail if price is invalid
+
+// ✅ With error handling
+const price = parseFloat(getField('price')) || 0;
+const quantity = parseFloat(getField('quantity')) || 0;
+const total = price * quantity;
+```
+
+**3. Infinite loops in onFieldChange**
+```javascript
+// ❌ Can cause infinite loop
+onFieldChange: function(fieldName, value) {
+    if (fieldName === 'total') {
+        setField('total', value * 1.1); // This will trigger onFieldChange again!
+    }
+}
+
+// ✅ Avoid triggering changes for calculated fields
+onFieldChange: function(fieldName, value) {
+    if (fieldName === 'quantity' || fieldName === 'price') {
+        const total = getField('quantity') * getField('price');
+        setField('total', total); // Only update when input fields change
+    }
+}
+```
+
+### Debug Techniques
+
+```javascript
+// Enable detailed logging
+onFieldChange: function(fieldName, value) {
+    console.group(`Field Change: ${fieldName}`);
+    console.log('New Value:', value);
+    console.log('Current Form Data:', {
+        quantity: getField('quantity'),
+        price: getField('price'),
+        total: getField('total')
+    });
+    
+    // Your calculation logic here
+    
+    console.groupEnd();
+}
+
+// Add validation checkpoints
+function calculateTotal() {
+    const quantity = getField('quantity');
+    const price = getField('price');
+    
+    console.log('Calculation inputs:', { quantity, price });
+    
+    if (isNaN(quantity) || isNaN(price)) {
+        console.error('Invalid inputs for calculation');
+        return;
+    }
+    
+    const total = quantity * price;
+    console.log('Calculated total:', total);
+    
+    setField('total', total.toFixed(2));
+}
+```
+
+---
+
+*This API reference covers all available JavaScript functionality in the Form Builder. For implementation examples and integration details, see the [Technical Guide](TECHNICAL_GUIDE.md) and [User Guide](USER_GUIDE.md).*
+
+Last updated: December 2024 
\ No newline at end of file
diff --git a/doc/form-builder/TECHNICAL_GUIDE.md b/doc/form-builder/TECHNICAL_GUIDE.md
index 2e12146..681a9bf 100644
--- a/doc/form-builder/TECHNICAL_GUIDE.md
+++ b/doc/form-builder/TECHNICAL_GUIDE.md
@@ -438,11 +438,11 @@ export const useFormBuilderStore = defineStore('formBuilder', {
     },
     
     formConfig: (state) => ({
-      id: state.formId,
-      uuid: state.formUUID,
-      name: state.formName,
-      description: state.formDescription,
-      components: state.formComponents
+        id: state.formId,
+        uuid: state.formUUID,
+        name: state.formName,
+        description: state.formDescription,
+        components: state.formComponents
     })
   },
   
@@ -912,8 +912,726 @@ const useVirtualScrolling = (components, containerHeight) => {
 }
 ```
 
+## JavaScript Execution Engine (FormScriptEngine)
+
+### Architecture Overview
+
+The FormScriptEngine component provides real-time JavaScript execution for dynamic form behavior, calculations, and conditional logic. It monitors form data changes and executes user-defined event handlers to create interactive forms.
+
+#### Core Components
+```
+components/
+├── FormScriptEngine.vue       # Main execution engine
+└── FormBuilderCanvas.vue      # Integration point for script execution
+pages/
+└── form-builder/
+    └── index.vue              # Form data handling and script triggering
+```
+
+### FormScriptEngine.vue Implementation
+
+```vue
+<template>
+  <!-- FormScriptEngine runs invisibly in the background -->
+  <div style="display: none;">
+    <!-- Debug info in development -->
+    <div v-if="isDev">
+      Script Engine Status: {{ isInitialized ? 'Active' : 'Initializing' }}
+    </div>
+  </div>
+</template>
+
+<script setup>
+import { ref, watch, nextTick, onMounted } from 'vue'
+
+// Component props
+const props = defineProps({
+  formData: {
+    type: Object,
+    required: true
+  },
+  script: {
+    type: String,
+    default: ''
+  }
+})
+
+// Reactive state
+const isInitialized = ref(false)
+const previousFormData = ref({})
+const scriptContext = ref(null)
+const handlers = ref({
+  onLoad: null,
+  onFieldChange: null
+})
+
+// Development mode detection
+const isDev = process.env.NODE_ENV === 'development'
+
+// Initialize script execution context
+const initializeScript = () => {
+  try {
+    if (!props.script.trim()) {
+      console.log('FormScriptEngine: No script provided')
+      return
+    }
+
+    // Create execution context with form functions
+    const context = {
+      setField: (fieldName, value) => {
+        console.log('setField called:', fieldName, '=', value)
+        
+        if (props.formData[fieldName] !== value) {
+          // Update form data reactively
+          props.formData[fieldName] = value
+          
+          // Emit update event for parent component
+          emit('fieldUpdate', { fieldName, value })
+        }
+      },
+      
+      getField: (fieldName) => {
+        const value = props.formData[fieldName]
+        console.log('getField called:', fieldName, '=', value)
+        return value
+      },
+      
+      console: console, // Allow console access
+      
+      // Add other safe global functions as needed
+      parseFloat: parseFloat,
+      parseInt: parseInt,
+      Date: Date,
+      Math: Math
+    }
+
+    // Execute script in isolated context
+    const scriptFunction = new Function(
+      'setField', 'getField', 'console', 'parseFloat', 'parseInt', 'Date', 'Math',
+      `
+        ${props.script}
+        
+        // Return the event handlers
+        return {
+          onLoad: typeof onLoad !== 'undefined' ? onLoad : null,
+          onFieldChange: typeof onFieldChange !== 'undefined' ? onFieldChange : null
+        }
+      `
+    )
+
+    // Execute script and extract handlers
+    const result = scriptFunction(
+      context.setField,
+      context.getField,
+      context.console,
+      context.parseFloat,
+      context.parseInt,
+      context.Date,
+      context.Math
+    )
+
+    handlers.value = result
+    scriptContext.value = context
+    
+    console.log('FormScriptEngine: Script initialized with handlers:', Object.keys(result))
+    
+    return true
+  } catch (error) {
+    console.error('FormScriptEngine: Script initialization error:', error)
+    return false
+  }
+}
+
+// Execute onLoad handler
+const executeOnLoad = async () => {
+  if (handlers.value.onLoad && typeof handlers.value.onLoad === 'function') {
+    try {
+      console.log('FormScriptEngine: Executing onLoad handler')
+      await handlers.value.onLoad()
+      console.log('FormScriptEngine: onLoad completed')
+    } catch (error) {
+      console.error('FormScriptEngine: onLoad execution error:', error)
+    }
+  }
+}
+
+// Execute onFieldChange handler
+const executeOnFieldChange = async (fieldName, value) => {
+  if (handlers.value.onFieldChange && typeof handlers.value.onFieldChange === 'function') {
+    try {
+      console.log('FormScriptEngine: Executing onFieldChange for:', fieldName)
+      await handlers.value.onFieldChange(fieldName, value)
+      console.log('FormScriptEngine: onFieldChange completed for:', fieldName)
+    } catch (error) {
+      console.error('FormScriptEngine: onFieldChange execution error:', error)
+    }
+  }
+}
+
+// Detect and trigger field changes
+const triggerFieldChangeDetection = () => {
+  const currentData = { ...props.formData }
+  const previousData = previousFormData.value
+  
+  // Find changed fields
+  const changedFields = []
+  
+  for (const fieldName in currentData) {
+    if (currentData[fieldName] !== previousData[fieldName]) {
+      changedFields.push({
+        name: fieldName,
+        value: currentData[fieldName],
+        oldValue: previousData[fieldName]
+      })
+    }
+  }
+  
+  if (changedFields.length > 0) {
+    console.log('FormScriptEngine: Detected field changes:', changedFields)
+    
+    // Execute handler for each changed field
+    changedFields.forEach(field => {
+      executeOnFieldChange(field.name, field.value)
+    })
+    
+    // Update previous data after processing
+    previousFormData.value = { ...currentData }
+  } else {
+    console.log('FormScriptEngine: No field changes detected')
+  }
+}
+
+// Watch for form data changes with enhanced detection
+watch(
+  () => props.formData,
+  (newData, oldData) => {
+    if (!isInitialized.value) return
+    
+    console.log('FormScriptEngine: Form data changed, checking for field changes...')
+    console.log('New data:', JSON.stringify(newData))
+    console.log('Previous data:', JSON.stringify(previousFormData.value))
+    
+    // Use nextTick to ensure DOM updates are complete
+    nextTick(() => {
+      triggerFieldChangeDetection()
+    })
+  },
+  { 
+    deep: true, 
+    flush: 'post' // Execute after DOM updates
+  }
+)
+
+// Initialize when component mounts
+onMounted(async () => {
+  console.log('FormScriptEngine: Component mounted, initializing...')
+  
+  // Initialize script context
+  const success = initializeScript()
+  
+  if (success) {
+    // Execute onLoad handler first
+    await executeOnLoad()
+    
+    // Set initial previousFormData AFTER onLoad execution
+    // This prevents initial setField calls from being detected as changes
+    await nextTick()
+    previousFormData.value = { ...props.formData }
+    
+    isInitialized.value = true
+    console.log('FormScriptEngine: Initialization complete')
+  } else {
+    console.error('FormScriptEngine: Initialization failed')
+  }
+})
+
+// Public method to manually trigger change detection
+const manualTrigger = () => {
+  console.log('FormScriptEngine: Manual trigger requested')
+  triggerFieldChangeDetection()
+}
+
+// Expose public methods
+defineExpose({
+  manualTrigger,
+  isInitialized
+})
+
+// Emit events
+const emit = defineEmits(['fieldUpdate'])
+</script>
+```
+
+### Integration with Form Builder
+
+#### Form Builder Canvas Integration
+```vue
+<!-- In FormBuilderCanvas.vue -->
+<template>
+  <div class="form-canvas">
+    <!-- Form components render here -->
+    <ComponentPreview 
+      v-for="component in formComponents"
+      :key="component.id"
+      :component="component"
+      :is-preview="isPreview"
+    />
+    
+    <!-- JavaScript execution engine -->
+    <FormScriptEngine
+      v-if="isPreview && formScript"
+      :form-data="previewFormData"
+      :script="formScript"
+      @field-update="handleScriptFieldUpdate"
+    />
+  </div>
+</template>
+
+<script setup>
+import FormScriptEngine from '~/components/FormScriptEngine.vue'
+
+// Handle script-triggered field updates
+const handleScriptFieldUpdate = ({ fieldName, value }) => {
+  console.log('Canvas: Script updated field:', fieldName, '=', value)
+  
+  // Update preview form data
+  previewFormData.value[fieldName] = value
+  
+  // Trigger UI refresh
+  nextTick(() => {
+    refreshFormComponents()
+  })
+}
+</script>
+```
+
+#### Main Form Builder Integration
+```vue
+<!-- In pages/form-builder/index.vue -->
+<script setup>
+// Enhanced FormKit input handler with script engine integration
+const handleFormKitInput = (event) => {
+  console.log('FormKit input event:', event)
+  
+  // Update preview form data
+  previewFormData.value = { ...event }
+  
+  // Trigger script engine change detection
+  if (formScriptEngineRef.value) {
+    nextTick(() => {
+      formScriptEngineRef.value.manualTrigger()
+    })
+  }
+}
+
+// Template ref for script engine
+const formScriptEngineRef = ref(null)
+</script>
+
+<template>
+  <div class="form-builder">
+    <!-- Canvas with integrated script engine -->
+    <FormBuilderCanvas
+      ref="formScriptEngineRef"
+      :form-script="formStore.currentForm?.script"
+      @form-kit-input="handleFormKitInput"
+    />
+  </div>
+</template>
+```
+
+### Event Handler API Reference
+
+#### onLoad Handler
+Executes once when the form loads. Use for initialization.
+
+```javascript
+onLoad: function() {
+    // Initialize default values
+    setField('status', 'active');
+    setField('created_date', new Date().toISOString().split('T')[0]);
+    
+    // Perform initial calculations
+    calculateInitialValues();
+}
+```
+
+#### onFieldChange Handler
+Executes when any field value changes.
+
+```javascript
+onFieldChange: function(fieldName, value) {
+    console.log('Field changed:', fieldName, 'New value:', value);
+    
+    // Handle specific field changes
+    switch(fieldName) {
+        case 'quantity':
+        case 'price':
+            updateTotal();
+            break;
+            
+        case 'country':
+            updateTaxRate(value);
+            break;
+    }
+}
+```
+
+### Error Handling and Debugging
+
+#### Script Execution Errors
+```javascript
+// Comprehensive error handling in script execution
+const executeHandler = async (handler, ...args) => {
+  try {
+    if (typeof handler === 'function') {
+      const result = await handler(...args)
+      return { success: true, result }
+    }
+    return { success: false, error: 'Handler is not a function' }
+  } catch (error) {
+    console.error('Script execution error:', error)
+    
+    // Emit error event for debugging
+    emit('scriptError', {
+      error: error.message,
+      stack: error.stack,
+      handler: handler.name || 'anonymous',
+      args
+    })
+    
+    return { success: false, error: error.message }
+  }
+}
+```
+
+#### Debug Mode Features
+```javascript
+// Enhanced logging in development mode
+const debugLog = (message, data) => {
+  if (isDev) {
+    console.log(`[FormScriptEngine Debug] ${message}`, data)
+  }
+}
+
+// Field change tracing
+const traceFieldChange = (fieldName, oldValue, newValue) => {
+  if (isDev) {
+    console.group(`Field Change: ${fieldName}`)
+    console.log('Old Value:', oldValue)
+    console.log('New Value:', newValue)
+    console.log('Timestamp:', new Date().toISOString())
+    console.groupEnd()
+  }
+}
+```
+
+### Performance Optimization
+
+#### Change Detection Optimization
+```javascript
+// Efficient change detection using shallow comparison
+const hasDataChanged = (newData, oldData) => {
+  const newKeys = Object.keys(newData)
+  const oldKeys = Object.keys(oldData)
+  
+  // Quick length check
+  if (newKeys.length !== oldKeys.length) return true
+  
+  // Value comparison
+  return newKeys.some(key => newData[key] !== oldData[key])
+}
+
+// Debounced change detection for rapid updates
+const debouncedChangeDetection = useDebounceFn(
+  triggerFieldChangeDetection, 
+  100 // 100ms debounce
+)
+```
+
+#### Memory Management
+```javascript
+// Cleanup when component unmounts
+onUnmounted(() => {
+  console.log('FormScriptEngine: Cleaning up...')
+  
+  // Clear references
+  handlers.value = null
+  scriptContext.value = null
+  previousFormData.value = null
+  
+  // Remove event listeners if any
+  cleanupEventListeners()
+})
+```
+
+### Security Considerations
+
+#### Script Sandboxing
+```javascript
+// Restricted execution context - only safe functions exposed
+const createSecureContext = () => {
+  return {
+    // Form manipulation functions
+    setField,
+    getField,
+    
+    // Safe global functions
+    console: {
+      log: console.log,
+      warn: console.warn,
+      error: console.error
+    },
+    
+    // Math and date functions
+    Math,
+    Date,
+    parseFloat,
+    parseInt,
+    isNaN,
+    
+    // String functions
+    String,
+    
+    // No access to:
+    // - window object
+    // - document object  
+    // - eval function
+    // - Function constructor
+    // - import/require
+  }
+}
+```
+
+#### Input Validation
+```javascript
+// Validate script before execution
+const validateScript = (script) => {
+  const dangerousPatterns = [
+    /eval\s*\(/,
+    /Function\s*\(/,
+    /window\./,
+    /document\./,
+    /import\s+/,
+    /require\s*\(/,
+    /fetch\s*\(/,
+    /XMLHttpRequest/
+  ]
+  
+  return !dangerousPatterns.some(pattern => pattern.test(script))
+}
+```
+
 ## Testing Strategy
 
+### JavaScript Engine Tests
+
+```javascript
+// FormScriptEngine unit tests
+describe('FormScriptEngine', () => {
+  let wrapper
+  let mockFormData
+  
+  beforeEach(() => {
+    mockFormData = ref({
+      quantity: 0,
+      price: 0,
+      total: 0
+    })
+    
+    wrapper = mount(FormScriptEngine, {
+      props: {
+        formData: mockFormData.value,
+        script: `
+          onLoad: function() {
+            setField('quantity', 1);
+            setField('price', 10);
+          }
+          
+          onFieldChange: function(fieldName, value) {
+            if (fieldName === 'quantity' || fieldName === 'price') {
+              const total = getField('quantity') * getField('price');
+              setField('total', total);
+            }
+          }
+        `
+      }
+    })
+  })
+  
+  test('should initialize script and execute onLoad', async () => {
+    await nextTick()
+    
+    expect(mockFormData.value.quantity).toBe(1)
+    expect(mockFormData.value.price).toBe(10)
+  })
+  
+  test('should execute onFieldChange when data changes', async () => {
+    await nextTick()
+    
+    // Simulate field change
+    mockFormData.value.quantity = 5
+    await nextTick()
+    
+    expect(mockFormData.value.total).toBe(50)
+  })
+  
+  test('should handle script errors gracefully', async () => {
+    const consoleErrorSpy = jest.spyOn(console, 'error').mockImplementation()
+    
+    const wrapper = mount(FormScriptEngine, {
+      props: {
+        formData: mockFormData.value,
+        script: `
+          onLoad: function() {
+            // Intentional error
+            undefinedFunction();
+          }
+        `
+      }
+    })
+    
+    await nextTick()
+    
+    expect(consoleErrorSpy).toHaveBeenCalled()
+    consoleErrorSpy.mockRestore()
+  })
+  
+  test('should validate and sanitize script input', () => {
+    const dangerousScript = `
+      onLoad: function() {
+        eval('alert("XSS")');
+        window.location = 'http://malicious.com';
+      }
+    `
+    
+    const isValid = wrapper.vm.validateScript(dangerousScript)
+    expect(isValid).toBe(false)
+  })
+})
+
+// Real-time calculation tests
+describe('Real-time Calculations', () => {
+  test('should update total when quantity changes', async () => {
+    const formData = ref({ quantity: 2, price: 15.99, total: 0 })
+    
+    const wrapper = mount(TestFormWithScript, {
+      props: { initialData: formData.value }
+    })
+    
+    // Change quantity
+    await wrapper.find('input[name="quantity"]').setValue('3')
+    await nextTick()
+    
+    expect(formData.value.total).toBe(47.97)
+  })
+  
+  test('should handle edge cases in calculations', async () => {
+    const formData = ref({ quantity: '', price: 'invalid', total: 0 })
+    
+    const wrapper = mount(TestFormWithScript, {
+      props: { initialData: formData.value }
+    })
+    
+    // Should handle invalid inputs gracefully
+    await nextTick()
+    expect(formData.value.total).toBe(0)
+  })
+})
+
+// Performance tests
+describe('FormScriptEngine Performance', () => {
+  test('should not trigger excessive re-renders', async () => {
+    const executeHandlerSpy = jest.spyOn(FormScriptEngine.methods, 'executeOnFieldChange')
+    
+    const wrapper = mount(FormScriptEngine, {
+      props: {
+        formData: { field1: '', field2: '', field3: '' },
+        script: `
+          onFieldChange: function(fieldName, value) {
+            console.log('Changed:', fieldName);
+          }
+        `
+      }
+    })
+    
+    // Make multiple rapid changes
+    for (let i = 0; i < 10; i++) {
+      wrapper.setProps({ formData: { field1: `value${i}`, field2: '', field3: '' } })
+      await nextTick()
+    }
+    
+    // Should be debounced/optimized
+    expect(executeHandlerSpy.mock.calls.length).toBeLessThan(10)
+  })
+})
+```
+
+### Integration Tests
+
+```javascript
+// Full form workflow tests with JavaScript
+describe('Form Builder with JavaScript Integration', () => {
+  test('should execute calculations in preview mode', async () => {
+    const wrapper = mount(FormBuilder)
+    
+    // Add form components
+    await wrapper.find('[data-component="number"]').trigger('click')
+    await wrapper.find('[data-component="number"]').trigger('click')
+    await wrapper.find('[data-component="number"]').trigger('click')
+    
+    // Configure fields
+    const components = wrapper.vm.formStore.formComponents
+    components[0].props.name = 'quantity'
+    components[1].props.name = 'price'
+    components[2].props.name = 'total'
+    
+    // Add JavaScript
+    wrapper.vm.formStore.currentForm.script = `
+      onFieldChange: function(fieldName, value) {
+        if (fieldName === 'quantity' || fieldName === 'price') {
+          const quantity = parseFloat(getField('quantity')) || 0;
+          const price = parseFloat(getField('price')) || 0;
+          setField('total', quantity * price);
+        }
+      }
+    `
+    
+    // Switch to preview mode
+    await wrapper.find('[data-testid="preview-toggle"]').trigger('click')
+    
+    // Input values
+    await wrapper.find('input[name="quantity"]').setValue('5')
+    await wrapper.find('input[name="price"]').setValue('19.99')
+    
+    await nextTick()
+    
+    // Check calculated total
+    const totalField = wrapper.find('input[name="total"]')
+    expect(totalField.element.value).toBe('99.95')
+  })
+  
+  test('should handle form builder to preview data flow', async () => {
+    const wrapper = mount(FormBuilder)
+    
+    // Build form with JavaScript
+    await addFormComponents(wrapper)
+    await addJavaScriptLogic(wrapper)
+    
+    // Test preview functionality
+    await wrapper.find('[data-testid="preview-button"]').trigger('click')
+    
+    // Verify script execution
+    expect(wrapper.find('.script-engine').exists()).toBe(true)
+    expect(wrapper.vm.isPreviewMode).toBe(true)
+    
+    // Test field interactions
+    await simulateUserInput(wrapper)
+    await verifyCalculations(wrapper)
+  })
+})
+```
+
 ### Unit Tests
 
 ```javascript
diff --git a/doc/form-builder/USER_GUIDE.md b/doc/form-builder/USER_GUIDE.md
index 1e4b246..79925e3 100644
--- a/doc/form-builder/USER_GUIDE.md
+++ b/doc/form-builder/USER_GUIDE.md
@@ -106,7 +106,7 @@ Perfect for collecting simple data:
 **Text Field**
 - Single-line text input
 - Smart width: Small (33%)
-- Use for: Names, titles, short answers
+  - Use for: Names, titles, short answers
 - Quick settings: Label, name, placeholder, required
 
 **Text Area**
@@ -119,7 +119,7 @@ Perfect for collecting simple data:
 - Numeric input with validation
 - Smart width: Narrow (25%)
 - Use for: Age, quantity, prices
-- Features: Min/max limits, step values
+  - Features: Min/max limits, step values
 
 **Email Field**
 - Email input with validation
@@ -131,7 +131,7 @@ Perfect for collecting simple data:
 - Secure password input
 - Smart width: Medium (50%)
 - Use for: Authentication forms
-- Features: Password masking, strength indicators
+  - Features: Password masking, strength indicators
 
 ### Selection Components
 For choosing from options:
@@ -151,7 +151,7 @@ For choosing from options:
 **Radio Group**  
 - Single choice from group
 - Smart width: Full (100%)
-- Use for: Exclusive choices, yes/no questions
+  - Use for: Exclusive choices, yes/no questions
 - Features: Button or traditional styles
 
 **Switch Toggle**
@@ -188,7 +188,7 @@ Specialized functionality:
 - Standard file input
 - Smart width: Wide (75%)
 - Use for: Document uploads, attachments
-- Features: File type restrictions, size limits
+  - Features: File type restrictions, size limits
 
 **File Drop Zone**
 - Drag & drop upload area
@@ -214,7 +214,7 @@ Form structure and organization:
 **Heading**
 - Section titles and organization
 - Smart width: Full (100%)
-- Use for: Form sections, categories
+  - Use for: Form sections, categories
 - Features: Multiple heading levels (H1-H6)
 
 **Paragraph**
@@ -311,7 +311,7 @@ Forms integrate seamlessly with the Process Builder for automated workflows:
 3. **Logical Grouping**: Use similar widths for related fields
 4. **Space Efficiency**: Let the system auto-optimize grid placement
 
-### User Experience  
+### User Experience
 1. **Clear Labels**: Use descriptive, action-oriented labels
 2. **Helpful Placeholders**: Provide examples in placeholder text
 3. **Progressive Disclosure**: Use sections for complex forms
@@ -362,7 +362,7 @@ Forms integrate seamlessly with the Process Builder for automated workflows:
 **Performance Issues**  
 - Reduce number of components
 - Simplify conditional logic
-- Clear browser cache
+   - Clear browser cache
 
 ### Getting Help
 - **Documentation**: Complete technical guides available
@@ -370,6 +370,281 @@ Forms integrate seamlessly with the Process Builder for automated workflows:
 - **Support**: Contact support team for assistance
 - **Community**: Join user community forums
 
+## JavaScript & Dynamic Calculations
+
+### Real-time Calculations
+The Form Builder supports powerful JavaScript-based calculations that update in real-time as users interact with your forms. This enables dynamic forms with automatic calculations, conditional logic, and interactive behavior.
+
+#### Key Features
+- **Real-time Updates**: Calculations execute instantly when users change field values
+- **onFieldChange Handlers**: Trigger custom logic when specific fields change
+- **setField Function**: Programmatically update field values from JavaScript
+- **Cross-field Dependencies**: Create complex relationships between form fields
+- **Calculation Templates**: Pre-built templates for common calculation patterns
+
+#### Basic Example
+```javascript
+// Form with real-time total calculation
+onLoad: function() {
+    console.log('Form loaded, setting up calculations...');
+    
+    // Initialize fields
+    setField('quantity', 1);
+    setField('price', 0);
+    setField('total', 0);
+}
+
+onFieldChange: function(fieldName, value) {
+    console.log('Field changed:', fieldName, '=', value);
+    
+    if (fieldName === 'quantity' || fieldName === 'price') {
+        // Get current values
+        const quantity = getField('quantity') || 0;
+        const price = getField('price') || 0;
+        
+        // Calculate and update total
+        const total = quantity * price;
+        setField('total', total.toFixed(2));
+        
+        console.log('Updated total:', total);
+    }
+}
+```
+
+### Available JavaScript Functions
+
+#### setField(fieldName, value)
+Updates a form field value and triggers the UI to refresh.
+```javascript
+// Set text field
+setField('user_name', 'John Doe');
+
+// Set number field
+setField('quantity', 5);
+
+// Set calculated field
+setField('total', 99.95);
+```
+
+#### getField(fieldName)
+Retrieves the current value of a form field.
+```javascript
+const userName = getField('user_name');
+const quantity = getField('quantity') || 0; // Default to 0 if empty
+```
+
+#### onLoad Event Handler
+Executes when the form first loads. Use for initialization and setting default values.
+```javascript
+onLoad: function() {
+    // Set default values
+    setField('country', 'USA');
+    setField('currency', 'USD');
+    
+    // Perform initial calculations
+    calculateTotals();
+}
+```
+
+#### onFieldChange Event Handler
+Executes whenever a user changes a field value. Receives fieldName and new value as parameters.
+```javascript
+onFieldChange: function(fieldName, value) {
+    switch(fieldName) {
+        case 'quantity':
+        case 'price':
+            updateTotal();
+            break;
+            
+        case 'country':
+            updateShippingOptions(value);
+            break;
+    }
+}
+```
+
+### Real-world Examples
+
+#### Invoice Calculator
+```javascript
+onLoad: function() {
+    // Initialize invoice fields
+    setField('quantity', 1);
+    setField('unit_price', 0);
+    setField('tax_rate', 8.5); // 8.5% tax
+    setField('subtotal', 0);
+    setField('tax_amount', 0);
+    setField('total', 0);
+}
+
+onFieldChange: function(fieldName, value) {
+    if (['quantity', 'unit_price', 'tax_rate'].includes(fieldName)) {
+        const quantity = parseFloat(getField('quantity')) || 0;
+        const unitPrice = parseFloat(getField('unit_price')) || 0;
+        const taxRate = parseFloat(getField('tax_rate')) || 0;
+        
+        const subtotal = quantity * unitPrice;
+        const taxAmount = (subtotal * taxRate) / 100;
+        const total = subtotal + taxAmount;
+        
+        setField('subtotal', subtotal.toFixed(2));
+        setField('tax_amount', taxAmount.toFixed(2));
+        setField('total', total.toFixed(2));
+    }
+}
+```
+
+#### Conditional Field Logic
+```javascript
+onFieldChange: function(fieldName, value) {
+    if (fieldName === 'subscription_type') {
+        if (value === 'premium') {
+            setField('premium_features', 'Available');
+            setField('support_level', '24/7 Priority');
+        } else {
+            setField('premium_features', 'Not Available');
+            setField('support_level', 'Standard Business Hours');
+        }
+    }
+}
+```
+
+#### Age Calculator
+```javascript
+onFieldChange: function(fieldName, value) {
+    if (fieldName === 'birth_date') {
+        const birthDate = new Date(value);
+        const today = new Date();
+        
+        let age = today.getFullYear() - birthDate.getFullYear();
+        const monthDiff = today.getMonth() - birthDate.getMonth();
+        
+        if (monthDiff < 0 || (monthDiff === 0 && today.getDate() < birthDate.getDate())) {
+            age--;
+        }
+        
+        setField('age', age);
+        
+        // Set eligibility based on age
+        if (age >= 18) {
+            setField('eligible', 'Yes');
+        } else {
+            setField('eligible', 'No');
+        }
+    }
+}
+```
+
+### Best Practices for JavaScript Forms
+
+#### Performance Optimization
+1. **Minimize Calculations**: Only calculate when necessary fields change
+2. **Use Default Values**: Provide fallbacks for empty fields
+3. **Debounce Heavy Operations**: For complex calculations, consider debouncing
+4. **Cache Results**: Store calculation results when appropriate
+
+#### Error Handling
+```javascript
+onFieldChange: function(fieldName, value) {
+    try {
+        if (fieldName === 'price') {
+            const price = parseFloat(value);
+            if (isNaN(price)) {
+                console.warn('Invalid price value:', value);
+                return;
+            }
+            
+            // Perform calculation
+            calculateTotal(price);
+        }
+    } catch (error) {
+        console.error('Error in field change handler:', error);
+    }
+}
+```
+
+#### Debugging Tips
+1. **Use Console Logging**: Add console.log statements to track execution
+2. **Check Field Names**: Ensure field names in code match form field names exactly
+3. **Validate Data Types**: Always parse and validate input values
+4. **Test Edge Cases**: Test with empty values, zero, and negative numbers
+
+### Form Templates with JavaScript
+
+#### CSS & JavaScript Test Form
+A comprehensive template demonstrating real-time calculations:
+
+**Field Structure:**
+- `user_name` (Text): User's name
+- `quantity` (Number): Quantity of items
+- `price` (Number): Price per item  
+- `total` (Number): Calculated total (read-only)
+
+**JavaScript Logic:**
+```javascript
+onLoad: function() {
+    console.log('Form loaded, initializing...');
+    setField('user_name', '');
+    setField('quantity', 1);
+    setField('price', 0);
+    setField('total', 0);
+}
+
+onFieldChange: function(fieldName, value) {
+    console.log('Field changed:', fieldName, '=', value);
+    
+    if (fieldName === 'user_name') {
+        console.log('User name updated to:', value);
+    }
+    
+    if (fieldName === 'quantity' || fieldName === 'price') {
+        const quantity = parseFloat(getField('quantity')) || 0;
+        const price = parseFloat(getField('price')) || 0;
+        const total = quantity * price;
+        
+        setField('total', total.toFixed(2));
+        console.log('Calculated total:', total);
+    }
+}
+```
+
+### Troubleshooting JavaScript Forms
+
+#### Common Issues
+
+**Calculations Not Updating**
+- Verify field names match exactly (case-sensitive)
+- Check browser console for JavaScript errors
+- Ensure `onFieldChange` handler is properly defined
+- Confirm form is in preview mode for testing
+
+**Initial Values Not Setting**
+- Make sure `onLoad` handler is defined
+- Check that `setField` calls use correct field names
+- Verify form data structure in browser developer tools
+
+**Console Errors**
+- **"getField/setField is not defined"**: JavaScript engine not properly initialized
+- **"Cannot read property"**: Field name doesn't exist or typo in field name
+- **"Unexpected token"**: Syntax error in JavaScript code
+
+#### Debugging Workflow
+1. **Open Browser Developer Tools** (F12)
+2. **Check Console Tab** for error messages
+3. **Add Debug Logging**:
+   ```javascript
+   onFieldChange: function(fieldName, value) {
+       console.log('=== Field Change Debug ===');
+       console.log('Field:', fieldName);
+       console.log('New Value:', value);
+       console.log('Current Form Data:', Object.keys(formData));
+       
+       // Your calculation logic here
+   }
+   ```
+4. **Test in Preview Mode** - JavaScript only executes in preview mode
+5. **Verify Field Names** - Use browser inspect element to confirm field name attributes
+
 ## Advanced Features
 
 ### Custom Components
diff --git a/pages/form-builder/index.vue b/pages/form-builder/index.vue
index 33294cb..e7c5e0f 100644
--- a/pages/form-builder/index.vue
+++ b/pages/form-builder/index.vue
@@ -196,6 +196,7 @@
             <!-- Preview Mode -->
             <div v-if="isPreview" class="form-container">
               <FormScriptEngine
+                ref="formScriptEngine"
                 :form-data="previewFormData"
                 :custom-script="formStore.formCustomScript"
                 :custom-css="formStore.formCustomCSS"
@@ -205,7 +206,13 @@
                 @field-validate="handleScriptFieldValidate"
               />
               
-              <FormKit type="form" @submit="handlePreviewSubmit" :actions="false" v-model="previewFormData">
+              <FormKit 
+                ref="previewForm"
+                type="form" 
+                @submit="handlePreviewSubmit" 
+                :actions="false" 
+                v-model="previewFormData"
+              >
                 <div class="grid-preview-container">
                   <template
                     v-for="(component, index) in formStore.formComponents"
@@ -495,26 +502,53 @@
               <div class="mb-4">
                 <h3 class="text-lg font-medium mb-2">Custom JavaScript</h3>
                 <p class="text-sm text-gray-600 mb-4">
-                  Write custom JavaScript to add dynamic behavior to your form. 
-                  Use <code class="bg-gray-100 px-1 rounded">this.getField('fieldName')</code> to access form fields.
+                  Write custom JavaScript to add dynamic behavior to your form. Scripts run securely in a sandboxed environment with access to form fields and utility functions.
                 </p>
                 
                 <!-- Helper Functions Reference -->
                 <div class="mb-4 p-3 bg-blue-50 rounded border border-blue-200">
                   <details>
-                    <summary class="text-sm font-medium text-blue-800 cursor-pointer">📚 Available Helper Functions</summary>
+                    <summary class="text-sm font-medium text-blue-800 cursor-pointer">📚 Core Functions</summary>
                     <div class="mt-2 text-xs text-blue-700 space-y-1">
-                      <div><code>this.getField('name')</code> - Get field value</div>
-                      <div><code>this.setField('name', value)</code> - Set field value</div>
-                      <div><code>this.hideField('name')</code> - Hide field</div>
-                      <div><code>this.showField('name')</code> - Show field</div>
-                      <div><code>this.disableField('name')</code> - Disable field</div>
-                      <div><code>this.enableField('name')</code> - Enable field</div>
-                      <div><code>this.validateField('name')</code> - Trigger field validation</div>
-                      <div><code>this.getAllFieldValues()</code> - Get all form values</div>
-          </div>
+                      <div><code>getField('name')</code> - Get field value</div>
+                      <div><code>setField('name', value)</code> - Set field value and trigger events</div>
+                      <div><code>hideField('name')</code> - Hide a field</div>
+                      <div><code>showField('name')</code> - Show a field</div>
+                      <div><code>disableField('name')</code> - Disable a field</div>
+                      <div><code>enableField('name')</code> - Enable a field</div>
+                      <div><code>validateField('name')</code> - Trigger field validation</div>
+                      <div><code>getAllFieldValues()</code> - Get all form values as object</div>
+                      <div><code>onFieldChange(['field1', 'field2'], callback)</code> - Listen for field changes</div>
+                    </div>
                   </details>
-      </div>
+                </div>
+                
+                <!-- User Interface Functions -->
+                <div class="mb-4 p-3 bg-green-50 rounded border border-green-200">
+                  <details>
+                    <summary class="text-sm font-medium text-green-800 cursor-pointer">🎨 UI & Notifications</summary>
+                    <div class="mt-2 text-xs text-green-700 space-y-1">
+                      <div><code>showSuccess('message')</code> - Display success notification</div>
+                      <div><code>showError('message')</code> - Display error notification</div>
+                      <div><code>showInfo('message')</code> - Display info notification</div>
+                      <div><code>querySelector('selector')</code> - Safe DOM querying within form</div>
+                    </div>
+                  </details>
+                </div>
+                
+                <!-- Utility Functions -->
+                <div class="mb-4 p-3 bg-purple-50 rounded border border-purple-200">
+                  <details>
+                    <summary class="text-sm font-medium text-purple-800 cursor-pointer">🛠️ Utilities</summary>
+                    <div class="mt-2 text-xs text-purple-700 space-y-1">
+                      <div><code>Math.*</code> - Mathematical functions (Math.round, Math.max, etc.)</div>
+                      <div><code>Date</code> - Date object for date/time operations</div>
+                      <div><code>Number()</code>, <code>String()</code>, <code>Array</code> - Type conversion</div>
+                      <div><code>setTimeout()</code>, <code>setInterval()</code> - Timing functions</div>
+                      <div><code>console.log()</code>, <code>console.warn()</code> - Debug logging</div>
+                    </div>
+                  </details>
+                </div>
               </div>
 
               <RsCodeMirror
@@ -522,21 +556,34 @@
                 language="javascript"
                 height="300px"
                 placeholder="// Example: Hide/show fields based on selection
-// this.onFieldChange('customer_type', (value) => {
+// onFieldChange('customer_type', (value) => {
 //   if (value === 'business') {
-//     this.showField('company_name');
-//     this.showField('tax_id');
+//     showField('company_name');
+//     showField('tax_id');
+//     showInfo('Business information fields are now visible');
 //   } else {
-//     this.hideField('company_name');
-//     this.hideField('tax_id');
+//     hideField('company_name');
+//     hideField('tax_id');
 //   }
 // });
 
-// Example: Calculate total
-// this.onFieldChange(['quantity', 'price'], () => {
-//   const qty = this.getField('quantity') || 0;
-//   const price = this.getField('price') || 0;
-//   this.setField('total', qty * price);
+// Example: Real-time calculations
+// onFieldChange(['quantity', 'price'], () => {
+//   const qty = Number(getField('quantity')) || 0;
+//   const price = Number(getField('price')) || 0;
+//   const total = Math.round((qty * price) * 100) / 100;
+//   setField('total', total);
+//   
+//   if (total > 1000) {
+//     showSuccess('Discount applied for orders over $1000!');
+//   }
+// });
+
+// Example: Conditional validation
+// onFieldChange('email', (value) => {
+//   if (value && !value.includes('@')) {
+//     showError('Please enter a valid email address');
+//   }
 // });"
               />
             </div>
@@ -598,8 +645,18 @@
               <div class="mb-4">
                 <h3 class="text-lg font-medium mb-2">Form Events</h3>
                 <p class="text-sm text-gray-600 mb-4">
-                  Configure when your custom scripts should run.
+                  Configure when your custom scripts should run. Field change events are detected automatically in real-time when users interact with form fields.
                 </p>
+                
+                <!-- Important Note -->
+                <div class="mb-4 p-3 bg-amber-50 rounded border border-amber-200">
+                  <div class="flex items-start">
+                    <Icon name="material-symbols:info" class="w-4 h-4 text-amber-600 mr-2 mt-0.5" />
+                    <div class="text-xs text-amber-700">
+                      <strong>Note:</strong> The "On Field Change" event must be enabled for <code>onFieldChange()</code> callbacks to work in your scripts.
+                    </div>
+                  </div>
+                </div>
               </div>
 
               <div class="space-y-4">
@@ -627,14 +684,20 @@
 
                 <div class="border rounded p-4">
                   <h4 class="font-medium mb-2">Script Execution Mode</h4>
-                  <div class="space-y-2">
-                    <label class="flex items-center">
-                      <input type="radio" v-model="formStore.scriptMode" value="safe" class="mr-2">
-                      <span class="text-sm">Safe Mode (Recommended) - Limited but secure</span>
+                  <div class="space-y-3">
+                    <label class="flex items-start">
+                      <input type="radio" v-model="formStore.scriptMode" value="safe" class="mr-2 mt-0.5">
+                      <div>
+                        <span class="text-sm font-medium text-green-700">Safe Mode (Recommended)</span>
+                        <p class="text-xs text-gray-600 mt-1">Scripts run in a secure sandbox with access only to form functions. Best for most use cases.</p>
+                      </div>
                     </label>
-                    <label class="flex items-center">
-                      <input type="radio" v-model="formStore.scriptMode" value="advanced" class="mr-2">
-                      <span class="text-sm">Advanced Mode - Full JavaScript access</span>
+                    <label class="flex items-start">
+                      <input type="radio" v-model="formStore.scriptMode" value="advanced" class="mr-2 mt-0.5">
+                      <div>
+                        <span class="text-sm font-medium text-orange-700">Advanced Mode</span>
+                        <p class="text-xs text-gray-600 mt-1">Provides broader JavaScript access but with security restrictions. Use with caution.</p>
+                      </div>
                     </label>
                   </div>
                 </div>
@@ -796,6 +859,7 @@
 
 <script setup>
 import { useFormBuilderStore } from "~/stores/formBuilder";
+import { nextTick } from 'vue';
 import FormBuilderHistory from "~/components/FormBuilderHistory.vue";
 import FormTemplatesModal from '~/components/FormTemplatesModal.vue';
 import FormBuilderFieldSettingsModal from '~/components/FormBuilderFieldSettingsModal.vue';
@@ -838,6 +902,8 @@ const showDropdown = ref(false);
 const showTemplatesModal = ref(false);
 const showFieldSettings = ref(false);
 const showFieldSettingsPanel = ref(false);
+const previewForm = ref(null);
+const formScriptEngine = ref(null);
 
 // Settings tabs configuration
 const settingsTabs = [
@@ -1617,118 +1683,127 @@ const previewFormData = ref({});
 
 // Initialize preview form data with default values
 watchEffect(() => {
-  const newFormData = {};
+  console.log('[FormBuilder] watchEffect for previewFormData initialization. Current form components:', formStore.formComponents.length);
+  const existingFormData = { ...previewFormData.value }; // Preserve current user inputs
+  let newDefaults = {};
+  let hasNewComponents = false;
+
   formStore.formComponents.forEach(component => {
     if (component.props.name) {
-      // Set default values based on component type
-      switch (component.type) {
-        case 'checkbox':
-          newFormData[component.props.name] = [];
-          break;
-          
-        case 'number':
-        case 'range':
-          newFormData[component.props.name] = component.props.value || 0;
-          break;
-          
-        case 'switch':
-          newFormData[component.props.name] = component.props.value !== undefined ? component.props.value : false;
-          break;
-          
-        case 'color':
-          newFormData[component.props.name] = component.props.value || '#3b82f6';
-          break;
-          
-        case 'hidden':
-          newFormData[component.props.name] = component.props.value || '';
-          break;
-          
-        case 'image-preview':
-        case 'info-display':
-        case 'button':
-          // These are display-only components and don't need form data values
-          break;
-          
-        case 'repeating-group':
-          // Initialize with one empty group or use minItems to determine how many initial groups
-          const initialGroups = [];
-          const minItems = component.props.minItems || 1;
-          
-          // Create the specified number of initial groups
-          for (let i = 0; i < minItems; i++) {
-            // Create an object with fields from the configuration
-            const group = {};
-            if (Array.isArray(component.props.fields)) {
-              component.props.fields.forEach(field => {
-                // Initialize each field with appropriate default value
-                switch (field.type) {
-                  case 'number':
-                    group[field.name] = 0;
-                    break;
-                  case 'checkbox':
-                    group[field.name] = [];
-                    break;
-                  case 'select':
-                    // If there's a default value in the options, use it
-                    const defaultOption = Array.isArray(field.options) && field.options.length > 0 
-                      ? field.options[0].value 
-                      : '';
-                    group[field.name] = field.value || defaultOption || '';
-                    break;
-                  default:
-                    group[field.name] = field.value || '';
-                }
-              });
+      // If field is not already in existingFormData, it's a new component or needs initialization
+      if (!existingFormData.hasOwnProperty(component.props.name)) {
+        hasNewComponents = true;
+        // Set default values based on component type
+        switch (component.type) {
+          case 'checkbox':
+            newDefaults[component.props.name] = [];
+            break;
+          case 'number':
+          case 'range':
+            newDefaults[component.props.name] = component.props.value || 0;
+            break;
+          case 'switch':
+            newDefaults[component.props.name] = component.props.value !== undefined ? component.props.value : false;
+            break;
+          case 'color':
+            newDefaults[component.props.name] = component.props.value || '#3b82f6';
+            break;
+          case 'hidden':
+            newDefaults[component.props.name] = component.props.value || '';
+            break;
+          case 'repeating-group':
+            const initialGroups = [];
+            const minItems = component.props.minItems || 1;
+            for (let i = 0; i < minItems; i++) {
+              const group = {};
+              if (Array.isArray(component.props.fields)) {
+                component.props.fields.forEach(field => {
+                  switch (field.type) {
+                    case 'number': group[field.name] = 0; break;
+                    case 'checkbox': group[field.name] = []; break;
+                    case 'select':
+                      const defaultOption = Array.isArray(field.options) && field.options.length > 0 ? field.options[0].value : '';
+                      group[field.name] = field.value || defaultOption || '';
+                      break;
+                    default: group[field.name] = field.value || '';
+                  }
+                });
+              }
+              initialGroups.push(group);
             }
-            initialGroups.push(group);
-          }
-          
-          newFormData[component.props.name] = initialGroups;
-          break;
-          
-        case 'dynamic-list':
-          // Initialize with default items from configuration
-          newFormData[component.props.name] = Array.isArray(component.props.defaultItems) 
-            ? [...component.props.defaultItems] 
-            : [];
-          break;
-          
-        case 'select':
-        case 'radio':
-          // For select and radio, initialize with first option value if available
-          if (Array.isArray(component.props.options) && component.props.options.length > 0) {
-            newFormData[component.props.name] = component.props.value || component.props.options[0].value;
-          } else {
-            newFormData[component.props.name] = '';
-          }
-          break;
-          
-        case 'date':
-        case 'time':
-        case 'datetime-local':
-          // Initialize with current date/time
-          newFormData[component.props.name] = component.props.value || '';
-          break;
-          
-        case 'file':
-          // Initialize file inputs as null
-          newFormData[component.props.name] = null;
-          break;
-          
-        default:
-          // For text, textarea, email, password, url, tel, etc.
-          newFormData[component.props.name] = component.props.value || '';
+            newDefaults[component.props.name] = initialGroups;
+            break;
+          case 'dynamic-list':
+            newDefaults[component.props.name] = Array.isArray(component.props.defaultItems) ? [...component.props.defaultItems] : [];
+            break;
+          case 'select':
+          case 'radio':
+            if (Array.isArray(component.props.options) && component.props.options.length > 0) {
+              newDefaults[component.props.name] = component.props.value || component.props.options[0].value;
+            } else {
+              newDefaults[component.props.name] = '';
+            }
+            break;
+          case 'date':
+          case 'time':
+          case 'datetime-local':
+          case 'file': // file inputs are handled by FormKit, typically initialized to null or specific file objects
+             newDefaults[component.props.name] = component.props.value || null;
+            break;
+          // image-preview, info-display, button don't usually hold data in previewFormData directly
+          case 'image-preview':
+          case 'info-display':
+          case 'button':
+            break;
+          default:
+            newDefaults[component.props.name] = component.props.value || '';
+        }
       }
     }
   });
-  previewFormData.value = newFormData;
+
+  // Only update previewFormData if it's the initial load (empty) or new components were added that need defaults
+  // This prevents overwriting user input when existing components change their props (which also triggers this watchEffect)
+  const isInitialLoad = Object.keys(previewFormData.value).length === 0 && Object.keys(newDefaults).length > 0;
+  
+  if (isInitialLoad || hasNewComponents) {
+    console.log('[FormBuilder] Initializing/merging preview form data. Initial load:', isInitialLoad, 'Has new components:', hasNewComponents);
+    previewFormData.value = { ...existingFormData, ...newDefaults };
+    console.log('[FormBuilder] Preview form data after init/merge:', previewFormData.value);
+  } else {
+    console.log('[FormBuilder] Skipping full previewFormData re-initialization to preserve user input.');
+  }
 });
 
 // Handle script-driven field changes
 const handleScriptFieldChange = ({ fieldName, value }) => {
-  previewFormData.value[fieldName] = value;
+  console.log('[FormBuilder] Script field change:', fieldName, '=', value);
+  
+  // Update the reactive form data
+  const newFormData = {
+    ...previewFormData.value,
+    [fieldName]: value
+  };
+  
+  previewFormData.value = newFormData;
+  
   // Make form data accessible to component previews
-  formStore.updatePreviewFormData(previewFormData.value);
+  formStore.updatePreviewFormData(newFormData);
+  
+  // Try to force FormKit form to update
+  nextTick(() => {
+    console.log('[FormBuilder] Updated form data:', newFormData);
+    
+    // Try to access the FormKit form node and update it directly
+    if (previewForm.value && previewForm.value.node) {
+      try {
+        previewForm.value.node.input(newFormData);
+        console.log('[FormBuilder] Force updated FormKit form');
+      } catch (error) {
+        console.warn('[FormBuilder] Could not force update FormKit form:', error);
+      }
+    }
+  });
 };
 
 // Handle script-driven field validation
@@ -1737,11 +1812,46 @@ const handleScriptFieldValidate = ({ fieldName }) => {
   console.log(`Validating field: ${fieldName}`);
 };
 
-// Make form data accessible to component previews
-watchEffect(() => {
+// Handle FormKit form input events
+const handleFormKitInput = (formData, node) => {
+  console.log('[FormBuilder] FormKit input event received!');
+  console.log('[FormBuilder] FormKit formData:', JSON.parse(JSON.stringify(formData)));
+  console.log('[FormBuilder] Current previewFormData before update:', JSON.parse(JSON.stringify(previewFormData.value)));
+  
+  // Update our reactive form data - this should trigger the FormScriptEngine watcher
+  const oldPreviewData = { ...previewFormData.value };
+  previewFormData.value = { ...formData };
+  
+  console.log('[FormBuilder] Updated previewFormData to:', JSON.parse(JSON.stringify(previewFormData.value)));
+  console.log('[FormBuilder] Did previewFormData actually change?', JSON.stringify(oldPreviewData) !== JSON.stringify(previewFormData.value));
+  
+  // Make form data accessible to component previews
   formStore.updatePreviewFormData(previewFormData.value);
+  
+  console.log('[FormBuilder] FormStore preview data updated to:', JSON.parse(JSON.stringify(formStore.previewFormData)));
+};
+
+// Make form data accessible to component previews (for UI rendering, not for triggering script engine)
+watchEffect(() => {
+  if (formStore) { // Ensure formStore is available
+    formStore.updatePreviewFormData(previewFormData.value);
+  }
 });
 
+// Watch for changes in previewFormData to trigger FormScriptEngine
+watch(() => previewFormData.value, (newData, oldData) => {
+  if (!isPreview.value) return; // Only in preview mode
+  
+  console.log('[FormBuilder] previewFormData watcher triggered!');
+  console.log('[FormBuilder] New data:', JSON.parse(JSON.stringify(newData)));
+  console.log('[FormBuilder] Old data:', oldData ? JSON.parse(JSON.stringify(oldData)) : 'undefined');
+  
+  // Update form store
+  formStore.updatePreviewFormData(newData);
+  
+  console.log('[FormBuilder] FormStore preview data updated to:', JSON.parse(JSON.stringify(formStore.previewFormData)));
+}, { deep: true, immediate: false });
+
 const navigateToManage = () => {
   // If already confirmed or no unsaved changes, navigate directly
   if (navigationConfirmed.value || !formStore.hasUnsavedChanges) {
diff --git a/prisma/json/json-schema.json b/prisma/json/json-schema.json
index 91cdbcb..4cdd83e 100644
--- a/prisma/json/json-schema.json
+++ b/prisma/json/json-schema.json
@@ -312,6 +312,35 @@
             "null"
           ]
         },
+        "customScript": {
+          "type": [
+            "string",
+            "null"
+          ]
+        },
+        "customCSS": {
+          "type": [
+            "string",
+            "null"
+          ]
+        },
+        "formEvents": {
+          "type": [
+            "number",
+            "string",
+            "boolean",
+            "object",
+            "array",
+            "null"
+          ]
+        },
+        "scriptMode": {
+          "type": [
+            "string",
+            "null"
+          ],
+          "default": "safe"
+        },
         "formStatus": {
           "type": "string",
           "default": "active"
diff --git a/stores/formBuilder.js b/stores/formBuilder.js
index 187a1b4..e0818d4 100644
--- a/stores/formBuilder.js
+++ b/stores/formBuilder.js
@@ -823,6 +823,11 @@ export const useFormBuilderStore = defineStore('formBuilder', {
       });
     },
     
+    // Update preview form data
+    updatePreviewFormData(data) {
+      this.previewFormData = { ...data };
+    },
+    
     // Optimize the grid layout by analyzing the current components
     // and adjusting their sizes to fill available spaces
     optimizeGridLayout() {