How Can I Access the Return Value of an Asynchronous AJAX Call?

Asynchronous AJAX Calls and Variable Return

In the context of dividing up your framework code into separate files, you encountered an issue where the return value of a function called via AJAX was not accessible. This confusion stems from the asynchronous nature of AJAX calls.

AJAX Calls: Asynchronicity Explained

AJAX (Asynchronous JavaScript and XML) functions operate asynchronously. This means that when an AJAX request is made, the function that makes the request does not wait for the response to complete before continuing execution. This allows other parts of the program to continue running in parallel while the AJAX request is in progress.

Function Return and AJAX

In the case of your get_data function, the return statement within the success callback function is not immediately executed when the function is called. Instead, it is executed only when the AJAX request is complete, and the response has been received.

Solution: Using Callbacks

To resolve this issue, you should provide a callback function to the get_data function. This callback will be executed when the AJAX request is complete, and the response data is available. The modified code would look like this:

function get_data(data, destination, callback) {
  if (lock_get == 0) {
    lock_get = 1;
    $.ajax({
      type: "POST",
      url: destination,
      async: true,
      data: data,
      success: function (data) {
        lock_get = 0;
        if (data && callback) {
          callback(data);
        }
      }
    });
  }
}

The calling code would then be modified to pass in a callback function:

get_data(data, destination, function (test) {
  notice(test);
});

This way, the response data can be handled within the callback function when the AJAX request is complete.

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