Javascript - ServiceNow

How is JavaScript linked with ServiceNow?

• ServiceNow is built on JavaScript.
• Almost all the backend scripts (like Business Rules, Script Includes, Scheduled Jobs) are written using Server-side JavaScript.
• Client-side scripts (like Client Scripts, UI Policies, Catalog Client Scripts) also use JavaScript to control what happens on the user’s browser.
• Glide API is ServiceNow’s built-in library written in JavaScript — it helps you easily interact with the ServiceNow database.

➔ In short: ServiceNow = JavaScript + ServiceNow's Glide API.

JavaScript Interview Questions (ServiceNow Focused)

1. How is JavaScript used in ServiceNow?

Answer:

JavaScript is used both on the client-side (browser) and server-side (server) in ServiceNow.

• Client-side scripting is used for form manipulation, field validation, and UI actions (example: Client Script, Catalog Client Script).
• Server-side scripting is used for database operations, automation, and backend processing (example: Business Rules, Script Includes).

2. What is a Client Script in ServiceNow?

Answer:

A Client Script is a piece of JavaScript that runs on the client’s browser when forms are loaded, changed, or submitted.

It is used to:

• Auto-populate fields
• Validate input before saving
• Display alerts or messages

Example:

function onLoad() {
  alert('Welcome to the form!');
}

3. What is a Business Rule in ServiceNow?

Answer:

A Business Rule is a server-side script that runs when records are inserted, updated, deleted, or queried.

It is used to:

• Automate tasks
• Enforce business logic
• Interact with the database

Example:

(function executeRule(current, gsn, gs) {
  current.short_description = 'Updated by Business Rule';
})(current, gsn, gs);

4. What is GlideRecord in ServiceNow?

Answer:

GlideRecord is a JavaScript class used to query, read, update, and delete records in ServiceNow tables (server-side).

Example:

var gr = new GlideRecord('incident');
gr.addQuery('priority', 1);
gr.query();
while (gr.next()) {
  gs.info(gr.number);
}

5. Difference between Client-side and Server-side scripting in ServiceNow?

Feature     | Client-side        | Server-side
Runs where? | User's browser     | ServiceNow server
Example     | Client Script      | Business Rule
Purpose     | Form behavior      | Database operations
API used    | GlideForm (g_form) | GlideRecord (gr), GlideSystem (gs)

6. What is a Script Include in ServiceNow?

Answer:

A Script Include is a reusable server-side JavaScript function or library that you can call from other scripts.

Example:

var HelloWorld = Class.create();
HelloWorld.prototype = {
  initialize: function() {},
  sayHello: function() {
    return "Hello, World!";
  },
  type: 'HelloWorld'
};

7. How do you call a Script Include from a Client Script?

Answer:

You can use GlideAjax to call server-side Script Includes from Client Scripts.

Example:

var ga = new GlideAjax('HelloWorld');
ga.addParam('sysparm_name', 'sayHello');
ga.getXMLAnswer(function(response){
  alert(response);
});

In Short: