jQuery Multiple getJSON requests

Question

My script needs to fetch several json files on https://graph.facebook.com/xxxx, and retrieve a certain field from each json, then calculate summation.

My problem is

Answer 1

It's not working as you are printing the result straight away, remember that the code where you concatenate the result is a callback so will fire after your alert.

On each callback you'll have to check if all have finished. replace the alert() call with your processing. :)

    var result = 0;
    var doneCount = 0;

    $.each(urls, function (i, url) {
        $.getJSON(url, function (json) {
            doneCount++;
            result += json.field1;
            if (doneCount == urls.length) {
                alert(result);
            }
        })
    });

Answer 2

Using jQuery 1.5 deferred objects:

Accumulate an array of the JQXHR objects returned by $.getJSON()

var jxhr = urls.map(function(url) {
    return $.getJSON(url, function(json) {
        result += json.field1;
    })
});

and only $.when they're all .done():

$.when.apply($, jxhr).done(function() {
    alert(result);
});

NB: this will accumulate result in the order that the AJAX calls complete, not in the order they're made.