Version: 4.9.0

Catalog Client Scripts

Guide for building ServiceNow Catalog Client Scripts (catalog_script_client) for service catalog items, record producers, and variable sets. These client-side scripts run in response to catalog form events such as onLoad, onChange, or onSubmit, enabling dynamic form behavior like field validation, visibility toggling, auto-populating fields from the current user, and user feedback messages.

Properties

For the complete property reference including all properties, types, and detailed descriptions, see the catalogclientscript-api documentation.

Script Types

onLoad

Runs when the form loads. Use for initial setup (field states, defaults, visibility).

onChange

Runs when a specific variable changes. Always guard with if (isLoading) return; to prevent execution during form load.

onSubmit

Runs on form submission. Return false to block submission. Avoid GlideAjax here — async calls won't complete before the form submits.

g_form API Reference

Method	Description
`getValue(fieldName)`	Get variable value
`setValue(fieldName, value)`	Set variable value
`setDisplay(fieldName, display)`	Show/hide variable
`setMandatory(fieldName, mandatory)`	Set mandatory state
`setReadOnly(fieldName, readOnly)`	Set read-only state
`clearValue(fieldName)`	Clear variable value
`hasField(fieldName)`	Check if field exists
`showFieldMsg(fieldName, message, type, scrollForm)`	Show field message
`hideFieldMsg(fieldName, clearAll)`	Hide field message
`addErrorMessage(message)`	Add banner error message
`clearOptions(fieldName)`	Clear all select options
`addOption(fieldName, value, label)`	Add a select option
`getReference(fieldName, callback)`	Get referenced record (legacy)

Note on getReference: Legacy convenience method. Works for simple lookups but GlideAjax is preferred for complex server-side logic. May make synchronous calls in some versions, which can freeze the UI.

GlideAjax

Use GlideAjax to call server-side Script Includes from client scripts. The client sends a request, the Script Include processes it, and returns a result via a callback.

GlideAjax Types — Quick Decision Guide

Method	Execution	Use When	Avoid When
`getXMLAnswer()`	Async	Simple lookups, returning a single value/string	You need the full XML response object
`getXML()`	Async	Need full XML response, complex response parsing	Simple value returns (use getXMLAnswer)
`getXMLWait()`	Sync	Almost never — legacy/global scope only	Scoped apps, any production code

GlideAjax Parameter Rules

All custom parameters must start with sysparm_. The first addParam call must always be sysparm_name with the method name.

ga.addParam("sysparm_name", "methodName"); // REQUIRED: always first
ga.addParam("sysparm_user_id", userSysId); // Custom param: prefix with sysparm_
ga.addParam("sysparm_category", selectedCat); // Custom param: prefix with sysparm_

Script Include (Server-Side Companion)

Every GlideAjax call requires a corresponding Script Include on the server. The Script Include must extend AbstractAjaxProcessor and be marked Client Callable.

Script Include Setup Checklist

Property	Value
Name	Must match the string in `new GlideAjax('ClassName')`
Client callable	Checked (required for GlideAjax access)
Extends	`global.AbstractAjaxProcessor`
Retrieve params	Use `this.getParameter('sysparm_param_name')`
Return data	Use `return` (simple string) or `return JSON.stringify(obj)` for objects

Script Include Security

Client callable = true: Only check this when the method is explicitly needed from the client.
Access controls: Runs in the logged-in user's session context. ACLs still apply to GlideRecord queries.
Input validation: Always validate parameters from this.getParameter(). Never trust client-side input.

Scripts on Variable Sets

Scope scripts to a variable set using variableSet and appliesTo: 'set' so they apply to all catalog items using that set. Always use hasField() checks since the variable may not exist on every item that includes the set.

Execution Order Note

When multiple variable sets are attached to a catalog item, scripts execute in the order the variable sets are listed on the item. If both a variable set script and an item-level script target the same variable, the item-level script runs last and takes precedence.

Catalog Client Script vs Standard Client Script

Aspect	Catalog Client Script	Standard Client Script
Scope	Catalog item or variable set	Table (e.g., Incident)
onChange target	Links to a variable	Links to a field
Context	Catalog ordering, RITM, Catalog Task forms	Table forms
Variable access	Direct by variable name	Use `variables.variable_name` prefix
Applies to	`item` or `set`	Specific table

Best Practices

Guard onChange: Always start with if (isLoading) return; to prevent execution on form load.
Use hasField() in variable set scripts: The variable may not exist on every catalog item using the set.
Avoid GlideAjax in onSubmit: Async calls won't complete before submission. Use onSubmit only for synchronous client-side validation.
Use g_form APIs, not DOM: Never use document.getElementById() or jQuery — it breaks across UI versions (UI16, Workspace, Portal).
Prefix for conflicts: If a variable name conflicts with a table field name, use variables.variable_name to reference the catalog variable.
Return JSON from Script Includes: Use JSON.stringify() on the server and JSON.parse() on the client for structured data.
Validate inputs in Script Includes: Never trust client-side parameters. Check for empty values, validate sys_id formats, and handle edge cases.
Use Now.include() for shared code: Extract reusable client logic into UI Scripts and load with Now.include('script_name') for maintainability.
Prefer getXMLAnswer over getXML: Simpler callback, less parsing code. Use getXML only when you need the full XML response.
Never use getXMLWait(): Synchronous, freezes the UI, not available in scoped apps. Always use async patterns.

Examples

Catalog Client Script -- onLoad

import { CatalogClientScript } from "@servicenow/sdk/core";
import { laptopRequest } from "../catalog-items/laptop-request.now";

CatalogClientScript({
  $id: Now.ID["laptop_onload"],
  name: "Laptop Request - OnLoad",
  script: Now.include("../../client/laptop-onload.js"),
  type: "onLoad",
  catalogItem: laptopRequest,
  active: true,
  appliesOnCatalogItemView: true
});

laptop-onload.js:

function onLoad() {
  g_form.setReadOnly("estimated_cost", true);
  g_form.setValue("estimated_cost", "$0");
  g_form.setMandatory("justification", true);
}

Catalog Client Script -- onChange

import { CatalogClientScript } from "@servicenow/sdk/core"
import { laptopRequest } from '../catalog-items/laptop-request.now'

CatalogClientScript({
  $id: Now.ID["laptop_type_change"],
  name: "Laptop Type - onChange",
  script: Now.include("../../client/laptop-type-change.js"),
  type: "onChange",
  catalogItem: laptopRequest,
  variableName: laptopRequest.variables.laptopType,
  active: true
});

laptop-type-change.js:

function onChange(control, oldValue, newValue, isLoading) {
  if (isLoading) return; // Always guard against initial load

  if (newValue === "developer") {
    g_form.setDisplay("accessories", true);
  } else {
    g_form.setDisplay("accessories", false);
    g_form.clearValue("accessories");
  }
}

Catalog Client Script -- onSubmit Validation

import { CatalogClientScript } from "@servicenow/sdk/core"
import { laptopRequest } from '../catalog-items/laptop-request.now'

CatalogClientScript({
  $id: Now.ID["laptop_validation"],
  name: "Laptop Request - Validation",
  script: Now.include("../../client/laptop-validation.js"),
  type: "onSubmit",
  catalogItem: laptopRequest,
  active: true
});

laptop-validation.js:

function onSubmit() {
  var justification = (g_form.getValue("justification") || "").trim();

  if (justification.length < 20) {
    g_form.showFieldMsg("justification", "Please provide at least 20 characters.", "error", true);
    g_form.addErrorMessage("Justification is too short.");
    return false;
  }

  return true;
}

Catalog Client Script -- onChange with GlideAjax

import { CatalogClientScript } from "@servicenow/sdk/core"
import { equipmentRepairItem } from '../catalog-items/equipment-repair'

CatalogClientScript({
  $id: Now.ID["asset_tag_lookup"],
  name: "Asset Tag - Warranty Lookup",
  script: Now.include("../../client/asset-tag-lookup.js"),
  type: "onChange",
  catalogItem: equipmentRepairItem,
  variableName: equipmentRepairItem.variables.asset_tag,
  active: true
});

asset-tag-lookup.js:

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

  if (!newValue) {
    g_form.clearValue("warranty_status");
    return;
  }

  var ga = new GlideAjax("global.AssetLookupUtil");
  ga.addParam("sysparm_name", "getWarrantyStatus");
  ga.addParam("sysparm_asset_tag", newValue);
  ga.getXMLAnswer(function (response) {
    if (!response) return;
    var info = JSON.parse(response);
    g_form.setValue("warranty_status", info.status);
  });
}