Execute callback at end of for-loop XMLHttpRequest

Question

This code loops through several webpages, finds links on each page, and puts those links into an array called linksArray . I've tried to execute a callback when the for-loop is on its last iteration (when x =45) and the jQuery find().each has finished searching through all of the last page for links.

For some reason, I'm not getting links from the very last page ( http://fakeURL.com/45 ). It seems that the callback function executes before the for-loop has gone through every webpage. Why is this happening and how do I fix it?

function linkSearch(callback)
{

    for(i = 0; i <= 45; i += 1) 
    {   
        ajaxCall(i);
    }

    var i;
    var linksArray = [];
    function ajaxCall (x)
    {
        var xhrs = new XMLHttpRequest();                                    
        xhrs.open("get", 'http://fakeURL.com/' + x, true);
        xhrs.onload = function()
        {       
            var doc = xhrs.response;
            var len = $(doc).length;    //will be used in telling when .each has gotten to the end of a page
            $(doc).find("a[href^='http://linksFromEachPage.com/links']").each(function(index, element)
            {
                //below is how I'm trying to callback the linksArray when the for-loop is on its last iteration and .each has finished on the last page
                thisVal = $(this).val();
                if (x == 45)
                {
                    if(parseInt(thisVal) != 0) 
                    {
                        if (index == len - 1) 
                        {
                            if($(doc).ajaxComplete)
                            {
                                callback(linksArray);
                            }
                        }
                    }
                }
                var url = $(this).attr('href');
                linksArray[x] = url;
            });
        }
        xhrs.responseType = 'document';
        xhrs.send();
    }

}

//and below is where the callback is called
linkSearch(function(theArray) 
{
    console.log(theArray);
});

Answer 1

Since your question is tagged with jQuery, here's a version of your code that uses jQuery for the ajax call and jQuery promises to keep track of when they are all done.

function linkSearch(callback) {
    var i, promises = [];
    for (i = 0; i <= 45; i++) {   
        promises.push(
           $.get({url:'http://fakeURL.com/' + i, dataType:'xml'})
        );
    }
    $.when.apply($, promises).then(function() {
        var linksArray = [];
        // process all results here
        for (i = 0; i < arguments.length; i++){
            $(arguments[i][0])
            .find("a[href^='http://linksFromEachPage.com/links']")
            .each(function(index, element) {
                var url = $(this).attr('href');
                linksArray.push(url);
            });
        }
        callback(linksArray);
    });
}