Decode JSON with jQuery / AJAX

Question

I'm trying to decode a JSON with jQuery. Here's what I get (for instance a class, here with one student):

"{"Students":[{"Name":John,"Grade":17,}],"TotalClass":17,"TotalCount":1,}"

here's what I do:

$j.ajax({
    type: 'POST',
    url: 'class.aspx/getClass',
    contentType: 'application/json; charset=utf-8',
    dataType: 'json',
    success: function (msg) {
        $j.each(msg, function (index, element) {
            alert(element.TotalClass);
        });
    },
});

It keeps saying undefined in the alert (but I recieve the right JSON). Any idea what I'm doing wrong?

Is that the actual json as returned by the server? Also, you have an extra comma on the second to last line. — user400654
– user400654, Commented Jun 13, 2012 at 15:43
If you receive the quotes you've put around the json, that can't be parsed. — Denys Séguret
– Denys Séguret, Commented Jun 13, 2012 at 15:46
Is that the exact JSON the server returns? Because it's invalid. — gen_Eric
– gen_Eric, Commented Jun 13, 2012 at 15:49
@dystroy I was under the impression that you can parse JSON with quotes, you just have to call JSON.parse(stringified_version); — kingsfoil
– kingsfoil, Commented Jul 15, 2014 at 19:25
I had a similar problem - the JSON response was not ,,translated'' to JS object. The reason was quite simple: I wrote datatype instead of dataType... So it's worthy to check such things. — jacek.ciach
– jacek.ciach, Commented Aug 25, 2014 at 6:32

Shyju · Accepted Answer · 2012-06-13 15:50:48Z

6

{"Students":[{"Name":John,"Grade":17,}],"TotalClass":17,"TotalCount":1,}

is not valid JSON !

Assuming you have a valid JSON like this

{
    "Students": [
        {
            "Name": "John",
            "Grade": "17"
        }
    ],
    "TotalClass": " 17",
    "TotalCount": "1"
}

You can access the values like this

alert("TotalClass : "+msg.TotalClass);
//loop thru students
$.each(msg.Students,function(index,item){
   alert(item.Name+ " - "+item.Grade)
});

Working sample : http://jsfiddle.net/ncbLF/5/

Use jsonlint to validate JSON

So your code can be simplified to

$.getJSON("class.aspx/getClass",function(msg){

    alert("TotalClass : "+msg.TotalClass);
    $.each(msg.Students,function(index,item){
        alert(item.Name+ " - "+item.Grade)
    });
});

answered Jun 13, 2012 at 15:50

Shyju

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Comments

gen_Eric · Accepted Answer · 2012-06-13 15:47:02Z

1

contentType is the type of the data sent to the server, not from. Remove that.

The JSON you included in the question. Is that the exact JSON the server returns? Because if it is, you don't need the $.each. You have an object, you should only need $.each to loop though an array of objects.

So, just try alert(msg.TotalClass).

Also, that JSON is invalid. You have an extra , after TotalCount, and after Grade. Also, John should be in double quotes.

answered Jun 13, 2012 at 15:47

gen_Eric

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Comments

thecodeparadox · Accepted Answer · 2012-06-13 15:59:22Z

1

Just try to alert

$j.each(msg, function (key, element) {
    alert(key); // output: Students, TotalClass..
    alert(element); //output: [{"Name":John,"Grade":17,}, 17..
});

Note

as you set dataType: 'json' so I think you don't need any additional parse effort and given JSON has error, don't know is it your written or originally sent from server.

And you don't need the line

contentType: 'application/json; charset=utf-8',

You valid json should look like:

{
    "Students": [
        {
            "Name": "John",
            "Grade": "17"
        }
    ],
    "TotalClass": " 17",
    "TotalCount": "1"
}

edited Jun 13, 2012 at 15:59

answered Jun 13, 2012 at 15:46

thecodeparadox

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