ServiceNow Client Script Functions

ServiceNow Client Scripts allow you to run JavaScript on the client-side (i.e., in the user's browser) to enhance the user interface experience. These scripts are typically used on forms and fields to manipulate UI elements, validate input, and auto-populate fields.

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🧠 Client Script Types

Type	Description
onLoad	Executes when a form is loaded.
onChange	Executes when a particular field's value changes.
onSubmit	Executes when a form is submitted.
onCellEdit	Executes when a cell is edited in a list (available in list editor).

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🔧 Common Client Script Functions

1. g_form — Manipulate Form & Fields

The g_form object is used to control form fields.

Function	Description
g_form.getValue('field_name')	Gets the value of a field.
g_form.setValue('field_name', value)	Sets the value of a field.
g_form.setDisplay('field_name', true/false)	Shows or hides a field.
g_form.setVisible('field_name', true/false)	(Alias of setDisplay)
g_form.setReadOnly('field_name', true/false)	Makes a field read-only or editable.
g_form.setMandatory('field_name', true/false)	Sets a field as mandatory or optional.
g_form.hideFieldMsg('field_name', true)	Hides the field-level messages.
g_form.showFieldMsg('field_name', 'message', 'info/error/warning')	Shows a message next to a field.
g_form.addInfoMessage('message')	Adds an informational message to the top of the form.
g_form.addErrorMessage('message')	Adds an error message to the top of the form.
g_form.clearMessages()	Clears all messages from the form.
g_form.getReference('field_name', callback)	Gets the referenced GlideRecord asynchronously.

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2. g_user — Current User Information

Function	Description
g_user.userID	Sys ID of the current user.
g_user.name	Full name of the current user.
g_user.firstName	First name of the current user.
g_user.lastName	Last name of the current user.
g_user.hasRole('role_name')	Returns true if the user has the specified role.

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3. g_scratchpad — Pass Server Info to Client

Useful when you want to pass data from a Script Include or business rule to the client script.

// Server Side Example:
g_scratchpad.someValue = 'Hello from server';

// Client Side:
alert(g_scratchpad.someValue);

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4. GlideAjax — Call Server Scripts from Client

Used to call server-side Script Includes.

var ga = new GlideAjax('MyScriptInclude');
ga.addParam('sysparm_name', 'myFunction');
ga.addParam('sysparm_input', g_form.getValue('field'));
ga.getXMLAnswer(function(response) {
  alert('Server returned: ' + response);
});

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5. g_form.isNewRecord()

Returns true if the form is in "New Record" mode (i.e., not yet saved).

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6. g_form.getSectionNames() and g_form.setSectionDisplay(section, visible)

Used to manipulate form sections (not commonly needed, but useful for dynamic forms).

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✨ Example: onChange Script

function onChange(control, oldValue, newValue, isLoading) {
  if (isLoading || newValue === '') return;

  if (newValue === 'closed') {
    g_form.setDisplay('closure_notes', true);
    g_form.setMandatory('closure_notes', true);
  }
}

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📌 Best Practices

• Use isLoading checks in onChange scripts to avoid unwanted behavior on form load.
• Avoid heavy operations in Client Scripts; offload logic to Script Includes via GlideAjax.
• Minimize the number of client scripts to improve performance.
• Use naming conventions like Client_OnLoad_ShowFields.

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Let me know if you'd like a downloadable .md file or examples for a specific use case (e.g., GlideAjax with Script Include).