Why Doesn\'t My AJAX Function Return a Variable, and How Can I Fix It Using Callbacks?

Variable Not Returned from AJAX Function

When dividing a framework into multiple files, you may encounter an issue where a variable does not get returned from an AJAX function. While the variable is not empty within the JS file, it appears empty in the main execution.

Original Function Pattern:

var lock_get = 0;

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

Execution:

var test = get_data(data, destination);
notice(test);

In the original approach, the get_data function attempts to return the result of the AJAX call, but fails due to the asynchronous nature of AJAX.

Solution: Using Callbacks

To resolve this issue, you can utilize callbacks. By passing a callback function to get_data, the result can be handled and returned:

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);
        }
      }
    });
  }
};

Execution (with Callback):

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

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