GlideForm.setValue() — ServiceNow API

g_form.setValue(fieldName, value, displayValue)→ void

beginnerTested on Xanadu

What It Does

The setValue() method modifies a field's value in the browser's form representation without submitting the record to the database. The method immediately updates the field's display value and internal form state, triggering any dependent UI policies or client scripts that monitor the changed field.

ServiceNow's form engine maintains two distinct values for each field: the internal value stored in the form's data model and the display value shown to users. When you call setValue(), the platform updates the internal value immediately and refreshes the field's visual representation. For reference fields, providing both the value (sys_id) and displayValue prevents an additional AJAX call to resolve the display name.

The method returns void and provides no indication of success or failure. Field validation occurs when the user attempts to save the form, not when setValue() executes. Invalid values will appear in the field until save-time validation rejects them.

Edge cases include setting values on non-existent fields (fails silently), setting reference field values without display values (triggers AJAX lookup), and setting choice field values with invalid options (displays the raw value). The method won't modify read-only fields that are enforced by UI policies, but will change fields that appear read-only due to ACL restrictions in the client context.

Related methods include getValue() for retrieval, clearValue() for emptying fields, and setDisplayValue() for updating only the visual representation without changing the underlying value.

When to Use This

Use setValue() when you need to programmatically populate form fields based on user actions, field changes, or external data lookups. Common scenarios include auto-populating related fields when a user selects a configuration item, setting default values based on the current user's preferences, or copying values from related records during form initialization.

Avoid setValue() when you need to save the changes immediately—use server-side Business Rules instead. Don't use it for complex validation logic that should prevent form submission; implement that in onSubmit() client scripts or server-side validation. Avoid setting values on fields that users should control directly, as this creates confusing user experiences where their input gets overwritten.

Return Value

The method returns void (undefined) in all cases, regardless of success or failure. You cannot determine from the return value whether the field update succeeded, the field exists on the form, or the value was valid for the field type.

To verify that setValue() succeeded, call getValue() immediately after to confirm the field contains the expected value. Check field existence with g_form.getElement(fieldName) before calling setValue() to avoid silent failures.

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Platform Behavior & Side Effects

Triggers onChange() client scripts for the modified field, potentially causing cascading field updates
Re-evaluates UI policies that depend on the changed field, potentially showing/hiding fields or making them mandatory
Does not write to the database until the user saves the form—all changes remain client-side only
Executes synchronously and immediately updates the DOM, making the change visible to users without delay
Reference fields without displayValue trigger AJAX calls to resolve the display name, introducing network latency
Does not trigger server-side Business Rules, ACLs, or notifications until form submission occurs
Marks the form as modified, enabling the browser's "unsaved changes" warning when navigating away

Parameters

Name	Type	Required	Description
fieldName	string	Yes	The field name to modify on the current form. Must match the column name exactly as defined in the dictionary. Case-sensitive and will fail silently if the field doesn't exist on the form.
value	string \| number \| boolean	Yes	The value to assign to the field. For reference fields, this must be the sys_id of the referenced record. For choice fields, use the choice value, not the label.
displayValue	string	No	Optional display value for reference fields. When provided, this text appears in the reference field instead of showing the sys_id. Required for reference fields to display human-readable values.

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Code Examples

Basic field updates with different data typesbasic

// Set text and choice field values
g_form.setValue('short_description', 'Network connectivity issue');
g_form.setValue('priority', '2');
g_form.setValue('state', '2');

// Set number and boolean values
g_form.setValue('business_criticality', '3');
g_form.setValue('made_sla', true);

// Clear a field by setting empty value
g_form.setValue('work_notes', '');

// Set date field (ISO format)
var today = new Date().toISOString().split('T')[0];
g_form.setValue('opened_at', today);

Basic field updates demonstrate the method's flexibility with different data types. Choice fields accept the internal value, not the display label, and boolean fields accept true/false values.

Reference field with proper display valueintermediate

// Wrong way - reference field shows sys_id to user
g_form.setValue('assigned_to', 'a8f98bb0eb32010045e1a5115206fe3a');

// Right way - provide both sys_id and display value
g_form.setValue('assigned_to', 
  'a8f98bb0eb32010045e1a5115206fe3a', 
  'Fred Luddy'
);

// When copying from another reference field
var assignedToValue = g_form.getValue('assigned_to');
var assignedToDisplay = g_form.getDisplayValue('assigned_to');

// Set caller to match assigned user
g_form.setValue('caller_id', assignedToValue, assignedToDisplay);

Reference fields require both the sys_id and display value to show human-readable text. Without the display value, users see the raw sys_id until an AJAX call resolves the name.

The classic mistake - setValue in infinite loopsadvanced

// WRONG: Creates infinite loop in onChange script
function onChange(control, oldValue, newValue, isLoading, isTemplate) {
    if (g_form.getValue('priority') == '1') {
        // This triggers another onChange event
        g_form.setValue('priority', '2');
    }
}

// RIGHT: Check if change is actually needed
function onChange(control, oldValue, newValue, isLoading, isTemplate) {
    if (newValue == '1' && g_form.getValue('urgency') != '2') {
        // Only set if urgency isn't already correct
        g_form.setValue('urgency', '2');
    }
}

Setting a field's value within its own onChange script creates infinite loops. Always check if the change is necessary and avoid modifying the same field that triggered the event.

Gotchas

Reference fields display the sys_id instead of the record name if you omit the displayValue parameter, confusing users.

Setting values on non-existent form fields fails silently with no error message or indication of failure.

Choice field values must use the internal choice value, not the display label—using display labels shows invalid raw text.

Calling setValue within an onChange script for the same field creates infinite loops that can crash the browser tab.

The method marks the form as dirty even if you set a field to its current value, triggering unsaved changes warnings.

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