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?

Answer 1

{"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)
    });
});