jQuery.ajax - always() not always running

Question

I'm using jQuery.ajax to make a REST call and retrieve some JSON. It's working as expected. However, when I force an error condition, such as an invalid URL, the always method does not fire. If I set crossDomain=false or dataType='json', then always does fire. But, I can't do that in my production code. If you set url='http://ip.jsontest.com/' then always fires. I created a small example to illustrate the problem:

var jqXHR = jQuery.ajax({ type: 'GET', async: false, cache: false, url: 'http://ip.jsontest.com.BADURL/', contentType: 'application/json; charset=UTF-8', crossDomain: true, dataType: 'jsonp' }) .done(function (data, textStatus, jqXHR) { console.log('Your IP is ' + data.ip); console.log('done was called'); }) .fail(function (jqXHR, textStatus, errorThrown) { console.log('fail was called'); }) .always(function (dataOrjqXHR, textStatus, jqXHRorErrorThrown) { console.log('always was called'); });

You can run this in the console at jquery.com which is using jQuery 1.9.1. I have the same behavior using jQuery 1.11.1. I need always to fire to handle times when the url is unavailable. I get the same behavior in IE11, Chrome 38 and FF 33. Am I doing something wrong or is this a bug? Thanks.

davidmdem · Accepted Answer · 2014-11-17 20:19:51Z

This is something that is known for JSONP calls. According to the $.ajax reference for error:

Note: This handler is not called for cross-domain script and cross-domain JSONP requests.

Also note that synchronous JSONP calls are not supported:

Cross-domain requests and dataType: "jsonp" requests do not support synchronous operation.

Workarounds typically involve either 1) setting a timeout for the call or 2) using a plugin to add more typical error functionality.

1) Setting a timeout (and async true)

var jqXHR = jQuery.ajax({ type: 'GET', async: true, cache: false, url: 'http://ip.jsontest.com.BADURL/', contentType: 'application/json; charset=UTF-8', crossDomain: true, dataType: 'jsonp', timeout: 2000 }) .fail(function (jqXHR, textStatus, errorThrown) { console.log('fail was called'); }) .done(function (data, textStatus, jqXHR) { console.log('Your IP is ' + data.ip); console.log('done was called'); }) .always(function (dataOrjqXHR, textStatus, jqXHRorErrorThrown) { console.log('always was called'); });

2) The jQuery JSONP plugin which adds error recovery features.

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