dataType: 'json' vs data: JSON.stringify(obj) in $.ajax

Question

I have this data structure:

var formValues = {
        TemporaryToken: a.userStatus.get("TemporaryToken"),
        MemorableWordPositionAndValues:[
            {
                Position: a.userStatus.get("MemorableWordPositions")[0],
                Value: this.$('[name="login-memorable-character-1"]').val()
            },
            {
                Position: a.userStatus.get("MemorableWordPositions")[1],
                Value: this.$('[name="login-memorable-character-2"]').val()
            },
            {
                Position: a.userStatus.get("MemorableWordPositions")[2],
                Value: this.$('[name="login-memorable-character-3"]').val()
            }
        ]
    }

And when I send it with $.ajax like so:

$.ajax({
        url:url,
        type:'PUT',
        //dataType:"json",
        data: JSON.stringify(formValues),
        success:function (data) {

        }
    });

It sends the request. However, if I send it like so:

$.ajax({
        url:url,
        type:'PUT',
        dataType:"json",
        data: formValues,
        success:function (data) {

        }
    });

I receive a 400 Bad Request. Is this a problem on the server or is JSON.stringify doing something different to just setting the dataType to 'json'?

user400654 · Accepted Answer · 2013-01-10 16:45:15Z

3

The server is expecting a JSON string, not form parameters. JSON.stringify converts your form parameters object/array into a JSON string, which is what your server appears to be expecting.

edited Jan 10, 2013 at 16:45

answered Jan 10, 2013 at 16:31

user400654

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4 Comments

benhowdle89 Over a year ago

How the F do you know it's going to ASP??

user400654 Over a year ago

I don't, i made an assumption due to the number of ASP questions that come here with the same problem, Was i completely off? Whether it's ASP or not, the simple fact is the server rejects it with a 400 response code if it isn't JSON according to your question.

benhowdle89 Over a year ago

ha, excellent. Well AFAIK it's going to a C# API, but the guys do use ASP as well!

user400654 Over a year ago

Updated to a non-server language specific answer, :-)

Community · Accepted Answer · 2017-05-23 12:09:24Z

It is still sending the request in the second attempt; it is simply that your server does not understand the request. That is because jQuery automatically processes the formValues data into a query string before sending the data. See the documentation:

data

Type: Object, String

Data to be sent to the server. It is converted to a query string, if not already a string. It's appended to the url for GET-requests. See processData option to prevent this automatic processing. Object must be Key/Value pairs. If value is an Array, jQuery serializes multiple values with same key based on the value of the traditional setting (described below).

So, you must use JSON.stringify(), or not use JSON. Note that setting processData to false won't help, since it will simply send the string [object Object] to your server. See also this question.

Tunaki · Accepted Answer · 2016-09-04 19:18:32Z

0

What about $.param()?

var my_data = {};
my_data.post_name = 'post_value';
$.ajax({
    url:'/post_url.php'
    data:$.param(my_data);
    ...
});

edited Sep 4, 2016 at 19:18

Tunaki

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answered Sep 4, 2016 at 15:43

Webmaster G

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