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 how to print out the result after all getJSON done? With below code it will prints 0. Feel free to suggest any better approaches.

var result = 0;
$.each(urls, function (i, url) {
    $.getJSON(url, function (json) {
        result += json.field1;
    })
});
alert(result);

Would you mind to post an example json object? Even though Facebook is the biggest social network side, not all users -like me- are registered at facebook. Thx — Reporter
– Reporter, Commented Apr 28, 2011 at 11:30

Alnitak · Accepted Answer · 2017-04-28 16:18:02Z

23

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.

edited Apr 28, 2017 at 16:18

answered Apr 28, 2011 at 11:30

Alnitak

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1 Comment

Jacinto Over a year ago

@Alnitak how can i handle, if the getJson failed, because the url dont exist?

nixon · Accepted Answer · 2011-04-28 11:30:06Z

3

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);
            }
        })
    });

answered Apr 28, 2011 at 11:30

nixon

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