name: servicenow-ui-forms user-invocable: false description: Manipulate form field state using g_form APIs — no server calls required. Covers field value get/set, mandatory/read-only/hidden control, inline validation and error messages, section and tab visibility, and form state checks. Use for dynamic/runtime field manipulation triggered by user actions (onChange, onLoad, onSubmit). For static field behavior based on conditions, prefer UI Policies instead — they load faster and don't require scripting. For scripts requiring GlideAjax server communication, use the servicenow-client-scripts skill. Trigger this skill whenever the user needs to control field visibility, mandatory state, read-only state, field values, or form messages in a ServiceNow client script without making server calls.

Customize UI Forms

Quick start

Field manipulation:

// Get/set values
g_form.setValue('field_name', 'new_value');
var value = g_form.getValue('field_name');

// Get display value (for reference fields)
var display = g_form.getDisplayValue('field_name');

// Set display value to avoid server calls
g_form.setValue('ref_field', 'sys_id', 'display_value');

Field properties:

// Mandatory
g_form.setMandatory('field_name', true);
var isMandatory = g_form.isMandatory('field_name');

// Read-only
g_form.setReadonly('field_name', true);
var isReadonly = g_form.isReadonly('field_name');

// Hidden
g_form.setHidden('field_name', true);
var isHidden = g_form.isHidden('field_name');

// Disabled
g_form.setDisabled('field_name', true);

Validation:

// Add validation error
g_form.setFieldError('field_name', 'Error message here');

// Clear validation error
g_form.clearFieldError('field_name');

// Form-level validation
function onSubmit() {
    if (g_form.getValue('priority') < 2 && !g_form.getValue('assignment_group')) {
        g_form.addErrorMessage('Assignment group required for high priority');
        return false;
    }
    return true;
}

Sections and tabs:

// Control section visibility
g_form.setVisible('section_name', true);

// Hide tab
g_form.switchToTab('tab_name');

// Set section label
g_form.setLabel('section_name', 'New Label');

Form state:

// Check if form is new record
var isNewRecord = g_form.isNewRecord();

// Get table name
var tableName = g_form.getTableName();

// Get form metadata
var control = g_form.getControl('field_name');

Common patterns

OnLoad initialization:

function onLoad() {
    var status = g_form.getValue('state');
    
    if (status === 'resolved') {
        g_form.setReadonly('resolution_details', true);
    }
    
    // Use g_scratchpad for server-pushed data
    if (g_scratchpad && g_scratchpad.requires_approval) {
        g_form.setMandatory('approval_notes', true);
    }
}

OnChange field dependencies:

function onChange(control, oldValue, newValue, isLoading) {
    if (isLoading) return;
    
    if (newValue === 'high') {
        g_form.setMandatory('assignment_group', true);
        g_form.setVisible('escalation_details', true);
    } else {
        g_form.setMandatory('assignment_group', false);
        g_form.setVisible('escalation_details', false);
    }
}

OnSubmit validation:

function onSubmit() {
    var category = g_form.getValue('category');
    var subCategory = g_form.getValue('sub_category');
    
    if (!subCategory && category === 'Hardware') {
        g_form.addErrorMessage('Sub-category required for Hardware');
        return false;
    }
    
    return true;
}

Best practices

• Use setValue(field, id, display) to avoid extra server calls
• Keep OnChange scripts focused and performant
• Use g_scratchpad to pass data from server without extra calls
• Always check isLoading to prevent redundant operations
• Use UI Policies for static field behavior — they load faster and don't require scripting
• Avoid DOM access; always use g_form API
• Test with different form layouts before production
• Validate user input client-side before submission
• Log form submissions for debugging

UI Policies vs g_form

Use UI Policies for:

• Conditional field visibility (show/hide) based on another field value
• Making fields read-only or editable based on conditions
• Marking fields as mandatory or optional based on conditions
• Clearing field values automatically
• Setting static field values
• Controlling related list visibility
• Static behavior based on encoded query conditions
• Performance-critical scenarios — UI Policies don't require client-side scripts

Use g_form for:

• Dynamic field manipulation triggered by user actions (onChange, onLoad, onSubmit)
• Complex logic requiring server communication via GlideAjax
• Custom validation with specific error messages
• Responsive behavior that changes based on user interactions
• Cascading field updates beyond simple conditional logic
• Form state checks and manipulation
• Setting field values dynamically from script logic

Performance tip: If your logic can be expressed as "if field X equals Y, then show field Z", always use a UI Policy. UI Policies are declarative and don't require async callbacks, making them significantly faster than client scripts that call g_form methods.

Example — Use UI Policy instead of g_form:

// ❌ NOT RECOMMENDED: Client script using g_form
function onChange(control, oldValue, newValue, isLoading) {
    if (newValue === 'hardware') {
        g_form.setMandatory('asset_tag', true);
        g_form.setVisible('serial_number', true);
    } else {
        g_form.setMandatory('asset_tag', false);
        g_form.setVisible('serial_number', false);
    }
}

// ✅ RECOMMENDED: UI Policy
UiPolicy({
  $id: Now.ID['category_hardware_policy'],
  table: 'incident',
  conditions: 'category="hardware"',
  actions: [
    { field: 'asset_tag', mandatory: true, visible: true },
    { field: 'serial_number', visible: true }
  ]
})

For complete UI Policy documentation, see the servicenow-fluent-development skill: UI-POLICY-API.md.

Key APIs

Examples

For working code examples covering field manipulation, UI actions, dynamic form behavior, and service catalog UI policies, see EXAMPLES.md

Reference

For g_form field manipulation, form event patterns, and performance optimization, see BEST_PRACTICES.md