When you log a JavaScript array after making a call using $.ajax, it may return an index

Question

When you log a JavaScript array after making a call using $.ajax, it may return an index

I am experiencing an issue with my array of 10 elements. When I log their key, value pairs in a loop, they are correctly ordered.

$.each( sArray, function(i, k) {
   log(i, k);

   // log(i, k) returns correctly 
   // [0] ELEMENT ONE
   // [1] ELEMENT TWO
   // [2] ELEMENT THREE

});

However, when I add an $.ajax call and try to log the array from there, the indices return in a random order (the order changes every time the page is refreshed)

$.each( sArray, function(i, k) {

   $.ajax({
       success: function(data){
          
          log(i, k);

          // returns unordered
          // [2] ELEMENT TWO
          // [1] ELEMENT ONE
          // [3] ELEMENT THREE
          // [5] ELEMENT FIVE
          // [4] ELEMENT FOUR
          // etc...
       }
    });
});

The key, value pairs match, but the order is unpredictable. Can someone clarify this behavior? Thank you!

javascript arrays ajax indexing unordered

Answer 1

Answer №1

Due to the asynchronous nature of AJAX, there is no guarantee on the order in which the operations will finish.

If maintaining a consistent order is essential, you should consider completing all AJAX operations before proceeding with any actions based on the array order. A possible solution could involve creating an array of promises and then waiting for all of them to resolve:

let requests = [];
$.each(array, function(index, element) {
  requests.push(
    $.ajax({
      //...//
      success: function(response){
        // Process the response data
        // You can add it as a property to the corresponding element
        // For instance:
        element.data = response;
      }
    })
  );
});

Promise.all(requests).then(function () {
  // At this point, all AJAX requests have been completed
  // You can now iterate over the array with the desired order:
  $.each(array, function(index, element) {
    console.log(index, element);
    // In this example, element.data contains the data fetched via AJAX
  });
});

Answer 2

Due to the asynchronous nature of AJAX, there is no guarantee on the order in which the operations will finish.

If maintaining a consistent order is essential, you should consider completing all AJAX operations before proceeding with any actions based on the array order. A possible solution could involve creating an array of promises and then waiting for all of them to resolve:

let requests = [];
$.each(array, function(index, element) {
  requests.push(
    $.ajax({
      //...//
      success: function(response){
        // Process the response data
        // You can add it as a property to the corresponding element
        // For instance:
        element.data = response;
      }
    })
  );
});

Promise.all(requests).then(function () {
  // At this point, all AJAX requests have been completed
  // You can now iterate over the array with the desired order:
  $.each(array, function(index, element) {
    console.log(index, element);
    // In this example, element.data contains the data fetched via AJAX
  });
});

When you log a JavaScript array after making a call using $.ajax, it may return an index

Answer №1

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