jQuery AJAX calls in for loop

Question

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Answer 1

The easiest way is to use a closure. Whenever you have something asynchronous in a loop, it is the same thing.

for (var i .....) {
  asynchronousFunction(function() {
    use(i);
  }
}

In this pseudocode snippet, the inner function captures the storage location referenced by i. The loop runs, the i increments to its final value, and then the async callbacks start getting called, all of them looking up the exact same location (not value).

The general solution is this:

for (var i .....) {
  (function (i) {
    asynchronousFunction(function() {
      use(i);
    });
  })(i);
}

i.e. wrap the whole contents of your loop in an self-executing function.

Here, the value of outer i gets passed into the wrapping self-executing anonymous function; this unique value's location gets captured by the async callback. In this way, each async gets its own value, determined at the moment the self-executing function is invoked.