jQuery AJAX calls in for loop

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.

The links in the comment section of the question tells you what is wrong in your code... but you can have a better solution than the once explained there.

Try $.each() to iterate through the list(assuming it is an array), so that the callback passed will create a separate closure for each iteration

$.each(linkList, function (i, item) {
    $.ajax({
        url: item.getAttribute("href"),
        cache: false
    }).done(function (html) {
        var hasAppended = false;
        if (html.indexOf('someStringOnGottenPage') != -1 && !hasAppended) {
            hasAppended = true;
            var id = item.getAttribute("href").substring(item.getAttribute("href").indexOf('='));
            $("#links a[href*='" + id + "']").append(' THIS PAGE CONTAINS SPECIFIED DATA');
        }
    });
})

---

If it is an jQuery object then use .each()

linkList.each(function (i, item) {
    var $item = $(item),
        href = $item.attr("href");
    $.ajax({
        url: href,
        cache: false
    }).done(function (html) {
        var hasAppended = false;
        if (html.indexOf('someStringOnGottenPage') != -1 && !hasAppended) {
            hasAppended = true;
            var id = href.substring(href.indexOf('='));
            $("#links a[href*='" + id + "']").append(' THIS PAGE CONTAINS SPECIFIED DATA');
        }
    });
})