How can I get jQuery to perform a synchronous, rather than asynchronous, Ajax request?

javascript

async-programming

ajax-requests

javascript-techniques

byNikita Barsukov·Jan 7, 2025

To execute a synchronous AJAX request in jQuery, we simply need to set the Ajax async setting to false:

$.ajax({
  type: 'GET',
  url: 'your-url',
  async: false, // "Your wish is my command!" - Browser probably
  success: function(data) {
    // Now you can enjoy your data... synchronously!
  }
});

Warning⚠️: Using synchronous AJAX could 'freeze' the browser. Be careful!

Explanation: What's with synchronous AJAX?

When you do a synchronous AJAX request, it stops all other JavaScript until the server responds. Now, wouldn't you be mad if you had to wait at a red light while the green light was on? That's essentially why it can be really bad. It leads to the web page becoming unresponsive until the data is returned, and who likes waiting nowadays, right?

Use Cases: When to use synchronous AJAX?

While it's generally advised to stick to asynchronous requests, there are times when you might need a synchronous request:

Legacy Systems: Sometimes, the systems were built before asynchronous programming was cool. In such cases, you might need to use synchronous AJAX to ensure consistency with old programming methods.
Data-dependency: When subsequent codes are heavily dependent on the data from the AJAX call, synchronous AJAX might seem tempting. But remember, with great power comes great responsibility!

Handling Synchronous AJAX: Like a Pro

If you must use synchronous AJAX, at least do it right! Here are some points to remember:

Be mindful of $.ajaxSetup({async:false}): This command tells jQuery "Hey, make all my AJAX calls synchronous". This could inadvertently make unrelated AJAX calls synchronous too, turning your UI into a waiting room!
Consider Better Approaches: Frame.js is a brilliant library that brings orderly queues to your asynchronous JavaScript operations. It makes your AJAX run in sequence without locking up the browser.

Possibilities beyond synchronous AJAX

You don't need to follow the traditional synchronous pattern to handle sequential logic. Here are some smart alternatives:

Promises: JavaScript Promises are like a restaurant reservation. Even if the table (data) isn't ready yet, you know you'll definitely get it (at least JavaScript hopes so!).
Async & Await: Have async functions wait for Promises to resolve before they proceed with their execution. This gives a pseudo-synchronous behavior and also keeps your code clean and easy to understand!

The Nitty-Gritty of `async: false`: Not all roses

Here are a few things you need to know about working with async: false:

Widget logic: Sometimes, the widget's action depends on the AJAX data. For this you need to ensure the beforecreate event returns false till the AJAX gets completed. Otherwise, the interface might build the widget before the data arrives.
URL & parameter encoding: Make sure the URL and parameters are encoded to avoid any quirky behaviours!
Testing: Changes to synchronous AJAX from asynchronous is like a major lifestyle change. Test your application thoroughly to ensure nothing breaks.