jQuery's ajaxSetup - I would like to add default data for GET requests only

Question

In a ajax-driven site I have added some default data using the ajaxSetup, ala this:

var revision = '159';
$.ajaxSetup({
    dataType: "text json",
    contentType: "application/x-www-form-urlencoded; charset=UTF-8",
    data: {
        r: revision
    }
});

This is to ensure cache-miss when a new revision is deployed and the frontend ask for html templates or json-data from the backend. The backend and frontend share the same revision number for this reason.

The problem is that the backend it somewhat unhappy about getting the parameter 'r' when the frontend does a PUT, POST or DELETE. Is there no way to tell jQuery's ajax that this data should only be used when doing GET requests and not when doing POST, PUT or DELETE requests.

UPDATE:

I tried the beforeSend function first, since I knew it. However changing settings.data was possible, but any change seemed to vanish when beforeSend returned. It may have been my fault... :-)

I have settled on the ajaxPreFilter instead. It was not easy as pie though. The options.data is not an object, but the result of $.param(object), so the first challenge was to un-parameterize it. I ended up with this:

var revision = '159';
$.ajaxPrefilter(function (options, originalOptions, jqXHR) {
    // do not send data for POST/PUT/DELETE
    if (originalOptions.type !== 'GET' || options.type !== 'GET') {
        return;
    }

    var data = originalOptions.data;
    if (originalOptions.data !== undefined) {
        if (Object.prototype.toString.call(originalOptions.data) === '[object String]') {
            data = $.deparam(originalOptions.data); // see http://benalman.com/code/projects/jquery-bbq/examples/deparam/
        }
    } else {
        data = {};
    }

    options.data = $.param($.extend(data, { r: revision }));
});

Looks like it is the intended behavior as explained in http://bugs.jquery.com/ticket/9757 — Ritesh, Jan 23 '13 at 22:46

score 36 · Accepted Answer · edited Sep 22 '15 at 20:43

36

Starting jQuery 1.5, you can handle this much more elegantly via Prefilters:

var revision = '159';
$.ajaxPrefilter(function (options, originalOptions, jqXHR) {
    // do not send data for POST/PUT/DELETE
    if(originalOptions.type !== 'GET' || options.type !== 'GET') {
        return;
    }

    options.data = $.extend(originalOptions.data, { r: revision });
});

edited Sep 22 '15 at 20:43

andrewtweber

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answered Aug 09 '11 at 14:46

Mrchief

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I'm with jQuery 1.6.4, I can only make it work like this: options.data = $.param($.extend(originalOptions.data, { r: revision })); – Morgan Cheng Mar 27 '12 at 06:55
1

@MorganCheng: Check if you're setting the right `contentType` and `processData` flag. jQeury would do the serialization accordingly. If your data is an array, you might want to check out `traditional` setting. – Mrchief Mar 27 '12 at 15:56
You have a trailing comma on your last line. – steve_c Sep 12 '13 at 17:45
jQuery 2.x seems `originalOptions.type` and `options.type` are lower cases, such as `options.type === 'post'` – WeizhongTu Nov 18 '16 at 08:29
@WeizhongTu That'd be a violation of the spec: https://www.w3.org/Protocols/rfc2616/rfc2616-sec5.html – Mrchief Nov 18 '16 at 17:23

Adam Terlson · Answer 2 · 2011-08-09T14:33:02.773

11

I think what you might be able to use is beforeSend.

var revision = '159';
$.ajaxSetup({
    dataType: "json",
    contentType: "application/x-www-form-urlencoded; charset=UTF-8",
    beforeSend: function(jqXHR, settings) {
        if(settings.type == "GET")
            settings.data = $.extend(settings.data, { ... });
        return true;
    }
});

jqXHR documentation

BeforeSend documentation as well as your settings available

I coded this blind, so I hope it gets you going in the right direction.

edited Aug 09 '11 at 14:33

answered Aug 09 '11 at 14:19

Adam Terlson

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What is the difference between $.ajaxPrefilter and beforeSend? – svlada Apr 29 '15 at 12:23
@svlada `$.ajaxSetup()` - Set default values for future Ajax requests. `$.ajaxPrefilter()` - Modify existing options before each request is sent. http://stackoverflow.com/a/29843893/2714931 – WeizhongTu Nov 18 '16 at 08:31

jQuery's ajaxSetup - I would like to add default data for GET requests only

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