🔄 GlideAjax in ServiceNow: Deep Dive with Real-Time Examples, Best Practices & Pro Tips

[Bhavesh Patil]

Hey #ServiceNowCommunity 👋

Ever needed to fetch server-side data from a client script without refreshing the page? Or wanted to access a Script Include from the client?

That’s exactly where GlideAjax comes in!

In this article, we’ll break down what GlideAjax is, how it works, the different ways to use it, and some real-world use cases and pro tips you won’t want to miss.

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💡 What is GlideAjax and Why Is It Important?

GlideAjax is a ServiceNow API that allows client-side scripts to call server-side Script Includes asynchronously using AJAX.

🚀 Why it’s important:

• Enables client-to-server communication without page reloads

• Prevents exposing sensitive logic directly on the client

• Improves user experience by fetching data dynamically (e.g., onChange, onLoad)

• Supports efficient architecture by reusing server-side business logic

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🧩 Types of GlideAjax (Explained with Real-Time Examples)

GlideAjax supports two primary ways of fetching data from a Script Include:

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🔹 1. getXML(callbackFunction)

Use this when you want to handle the response as an XML object and do more custom parsing.

// Client Script
var ga = new GlideAjax('UserInfoAjax');
ga.addParam('sysparm_name', 'getManagerName');
ga.getXML(handleResponse);

function handleResponse(response) {
   var answer = response.responseXML.documentElement.getAttribute("answer");
   alert("Manager Name: " + answer);
}

// Script Include
var UserInfoAjax = Class.create();
UserInfoAjax.prototype = {
    initialize: function() {},
    
    getManagerName: function() {
        var user = gs.getUserID();
        var gr = new GlideRecord('sys_user');
        gr.get(user);
        return gr.manager.name;
    },

    type: 'UserInfoAjax'
};

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🔹 2. getXMLAnswer(callbackFunction)

Use this when your Script Include returns only a single value, and you want a simplified response (string only).

// Client Script
var ga = new GlideAjax('UserInfoAjax');
ga.addParam('sysparm_name', 'getDepartment');
ga.getXMLAnswer(function(response) {
   g_form.setValue('department', response);
});

// Script Include
var UserInfoAjax = Class.create();
UserInfoAjax.prototype = {
    initialize: function() {},
    
    getDepartment: function() {
        return gs.getUser().getDepartmentID();
    },

    type: 'UserInfoAjax'
};

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🔄 Difference Between getXML() and getXMLAnswer()

Feature getXML() getXMLAnswer()

Response Type	Full XML object	Direct string value
Parsing Required	Yes (extract from responseXML)	No (response is answer directly)
Best For	Complex structured data	Simple single-string responses
Code Simplicity	More verbose	Short and cleaner
Performance	Slightly heavier	Faster and lightweight

🟢 Prefer getXMLAnswer() when you only need a string or simple value.
🟡 Use getXML() for structured responses or multiple values (you can encode them as JSON strings too).

Absolutely! Here's the refined and formatted version of your "Types of GlideAjax" section, with your points clearly structured into a professional and community-friendly explanation:

There are two types of GlideAjax executions based on how they interact with the server:

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🔹 1. Synchronous GlideAjax

• Waits for the server response before continuing further execution

• Blocks the UI thread — can cause form slowness or freezing

• Not recommended for modern UI/UX due to performance impact

• Executed using: getXMLWait()

• Suitable only when immediate response is critical (rare cases)

var ga = new GlideAjax('MyScriptInclude');
ga.addParam('sysparm_name', 'getSomething');
var response = ga.getXMLWait();  // Synchronous
var answer = response.responseXML.documentElement.getAttribute("answer");

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🔹 2. Asynchronous GlideAjax

• Does not wait for server response

• Execution continues — once response is ready, a callback function is invoked

• Keeps UI responsive and works in parallel with client/server

• Executed using: getXML() or getXMLAnswer()

• Preferred approach in almost all scenarios

var ga = new GlideAjax('MyScriptInclude');
ga.addParam('sysparm_name', 'getSomething');
ga.getXMLAnswer(function(response) {
    console.log("Server response: " + response);
});

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🆚 Key Differences Between Synchronous vs Asynchronous GlideAjax : 

Feature	Synchronous (getXMLwait())	Asynchronous (getXML/ getXMLAnswer())
Waits for response	Yes	No
Blocks UI thread	Yes	No
Performance	Slower (not recommended)	Faster and efficient
Parallel Execution	❌ No	✅ Yes
Use Case	Critical need for immediate data	Dynamic form behavior, data fetch, validations
Callback Required	❌ No	✅ Yes

🟢 Recommendation: Always prefer Asynchronous GlideAjax for better performance and user experience.

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✅ Best Practices for GlideAjax

✅ Keep your Script Includes clean and focused on single responsibility
✅ Always check "Client Callable" in Script Include if calling from client
✅ Use getXMLAnswer() for simpler logic
✅ Minimize server calls — don't call GlideAjax in loops
✅ Avoid sensitive logic in client-callable Script Includes
✅ Use naming conventions like SI_<Module>_<Purpose> for clarity
✅ Return only what you need — avoid bloated responses

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💼 Real-Time Use Cases of GlideAjax

1. 🔄 Auto-populate Manager field when user is selected on a form

2. ✅ Validate custom business logic before submitting a record

3. 🔍 Fetch user roles or department dynamically during form load

4. 📋 Get count of related records for display on UI

5. 🔒 Server-side permission checks before showing UI actions

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💡 Pro Tips

🔹 Use JSON.stringify() and JSON.parse() if you need to return complex data structures via getXMLAnswer()
🔹 Return only what's needed — it keeps the client fast
🔹 Log server-side errors using gs.error() to make debugging easier
🔹 Test your Script Include logic independently before calling via client
🔹 Wrap GlideAjax inside custom utility functions to simplify reuse

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🏁 Final Thoughts

GlideAjax bridges the gap between client and server in ServiceNow. Used right, it can make your applications dynamic, efficient, and secure. Whether you're building custom forms, UI Actions, or form validations—mastering GlideAjax is a must for any ServiceNow developer.

Have any creative use cases or challenges using GlideAjax? Drop them in the comments — let’s grow together! 🚀

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