Wait until jquery ajax request is done and return value

Question

I want to wait until ajax call complete and return the value.

function isFileExists(url) {
    var res = false;
    $.ajax({
        type: "GET",
        async: false,
        url: url,
        crossDomain: true,
        dataType: "script",
        success: function () {
            res = true;
        },
        error: function () {
            res = error;
        },
        complete: function () {

        }
    });
    return res; //It is always return false
}

I want to return the value "true/error"

Please help me.

consider using jquery tag instead of javascript next time, its gonna make it more specific and save people time. Thank You — Toping, Mar 06 '13 at 13:25

Explosion Pills · Answer 1 · 2013-03-06T13:33:42.903

10

You can't do this. That's not how ajax works. You can't depend on the ajax request completing at any given time ... or ever completing. Any work you need to do that is based on the ajax request must be done in the ajax callbacks.

jQuery makes it easy to bind callbacks (because jqXHR returned by jQuery's ajax methods implements Deferred):

var jqXHR = $.ajax({/* snip */});

/* millions of lines of code */

jqXHR.done(function () {
    console.log('true');
}).fail(function () {
    console.log('false');
});

P.S. you can do what you want to do if you set async to false, but that locks up the browser while the request runs. Don't do it. Then you just have jax.

EDIT: You can't combine crossDomain: true and async: false. Cross Domain must be asynchronous.

edited Mar 06 '13 at 13:33

answered Mar 06 '13 at 13:24

Explosion Pills

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3

you mean `async` to `false` – Gabriele Petrioli Mar 06 '13 at 13:26
@ExplosionPills : I am calling isFileExists(url) from another function. How can I call jqXHR – Sagar Mar 06 '13 at 13:33
@Sagar in `isFileExists` do `return $.ajax(...)`. Then you can use it like `isFileExists(url).done(function () {` – Explosion Pills Mar 06 '13 at 13:35
@ExplosionPills isFileExists(url).done(function () { //here I want result value how can I get it }); – Sagar Mar 06 '13 at 13:38
@Sagar is the result value sent from the server? Then just do `.done(function (resultValue) {` – Explosion Pills Mar 06 '13 at 13:42
@ExplosionPills when I try isFileExists(url).done(function (returnval) { alert(returnval+"===saa"); }); it is saying isFileExists(url).done() not a funtion – Sagar Mar 06 '13 at 13:45
@Sagar can you post your `isFileExists` function on jsfiddle or something? – Explosion Pills Mar 06 '13 at 13:48
@Sagar the fiddle won't work because the url is not defined. Or are you saying it's not working in your production code. *Please* take some initiative and try to debug the issue on your own; it's not that complicated – Explosion Pills Mar 06 '13 at 14:31

net892z · Answer 2 · 2013-03-06T14:13:27.813

maybe this will work for you:

function isFileExists(url, init) {
    var res = null;
    var _init = init || false;

    if (!_init) {
        _init = true;
        $.ajax({
             type: "GET",
             url: url,
             crossDomain: true,
             dataType: "script",
             success: function () {
                 res = true;
             },
             error: function () {
                 res = 'error';
             },
             complete: function () {

             }
        });
    }

    if (res==null) {
        setTimeout(function(){ isFileExists(url, _init); }, 100);
    } else {
        return res;
    }
}

I tested it briefly, but not cross domain.

Yes it should be called until the ajax request has been resolved. Try adding the 'timeout' setting to the ajax call, setting it to 1 minutes (maybe), as means to escape. — net892z, Mar 06 '13 at 14:20

score 0 · Answer 3 · answered Dec 28 '20 at 13:49

Try this code. it worked for me.

 function getInvoiceID(url, invoiceId) {
        return $.ajax({
            type: 'POST',
            url: url,
            data: { invoiceId: invoiceId },
            async: false,
        });
    }
    function isInvoiceIdExists(url, invoiceId) {
        $.when(getInvoiceID(url, invoiceId)).done(function (data) {
            if (!data) {

            }
        });
    }

Wait until jquery ajax request is done and return value

3 Answers3