JavaScript Promises - Using promises in ServiceNow Scripting Part 3

[RAMANA MURTHY G]

Hello Community, 

To use JavaScript Promises in ServiceNow scripting—both for platform scripting (server-side) and Service Portal scripting (client-side)—you need to understand when and where native JavaScript Promises are supported, and how to structure your code to handle asynchronous operations accordingly.

Check my previous articles about JavaScript Promises

JavaScript Promises/Synchoronous/Asynchronous - Part 1 

Understanding Promises in JavaScript – Part 2 

A Promise represents an asynchronous operation. It can be in one of three states: pending, fulfilled, or rejected. Promises are particularly useful for handling AJAX calls, GlideAjax, or long-running code where you don’t want to block execution.

Using Promises in ServiceNow Platform Scripting (Server-Side)

By default, server-side scripts in ServiceNow (like Business Rules, Script Includes) run synchronously. ECMAScript5 is supported, but native Promises may not be fully available.

ServiceNow doesn’t provide direct native Promises server-side, but libraries and patterns exist for similar behavior using callback functions.

• Write a Script Include with asynchronous logic.

• Use callback functions to simulate Promise chains, or use third-party libraries if allowed.

we can define a script include to queue jobs with callbacks, essentially mimicking Promise behavior, especially with the GlideAjax mechanism if going client-to-server or using GlideRecord in scripts.

Because native Promises are not fully supported server-side in ServiceNow, most Promise-based models in ServiceNow use client-side JavaScript and Service Portal scripting.

Using Promises in Service Portal Scripting (Client-Side)

Service Portal widgets run in the browser and fully support modern JavaScript features, including native Promises.

Using widget Client Script:

Suppose we want to fetch data from the server using server.update()  [returns a Promise]:

// In the Service Portal widget client controller
function getDataFromServer() {
    // this.server.update() returns a Promise
    return this.server.update();
}

getDataFromServer().then(function(response) {
    // handle successful response
    console.log("Data received:", response);
}).catch(function(error) {
    // handle error
    console.error("An error occurred:", error);
});

Key points:

• Use native Promises in Service Portal client code for AJAX calls, widgets, and user-side logic
• Server-side code: While native Promises are not fully available, you can structure code using callbacks or patterns from libraries.
• Best practice: Always chain .then() and .catch() for error handling and code clarity.

This approach ensures you write asynchronous, non-blocking code in ServiceNow, handling real-world scenarios like processing user input, chaining API calls, or updating the UI dynamically based on server responses.

🙏 If you found this article helpful:

• Please mark it as Helpful
• Feel free to share your thoughts, suggestions, or questions in the comments

Thanks for reading! 😊

Ramana Murthy G
ServiceNow Developer

Note: I used ChatGPT to help with the restructuring and phrasing of the article body to ensure better clarity and flow.