JSON string evaluation with JavaScript, and getting it's value with JavaScript

Question

I have this case (a JSON string returned by my server):

{"success": true, "users": [1, 3, 4, 8]}

However, when using this kind of request, I'd get that response as a "string":

var availableUsers = $.ajax({
    url: absPath + '/users/findUsers',
    type: 'POST',
    data: {contents: $('#messageTo').val()},
    dataType: 'json',
    async: false
}).responseText;

With: alert(typeof(availableUsers)); I'd get: string return value from typeof.

When doing this:

window.eval(availableUsers); It won't be evaluated as expected, to a JavaScript Object.

How can I get the valid JSON response (using, async: false) converted to a JavaScript accessable Object or how can I propertly evaluate the string returned from the server?

Thanks!

Check the content type header returned from the request to /users/findUsers — a'r, Nov 22 '11 at 18:05
possible duplicate of [how to parse json in javascript](http://stackoverflow.com/questions/4935632/how-to-parse-json-in-javascript) — Felix Kling, Nov 22 '11 at 18:05
Is there a reason you aren't using a `success` callback here? Even with `async:true`, this would likely be a) more legible, and b) more likely to do what you expect. I don't think jQuery's automatic JSON-parsing will kick in with `.responseText`. — nrabinowitz, Nov 22 '11 at 18:07

score 0 · Accepted Answer · edited May 23 '17 at 11:48

0

try setting the content type of your request to application/json read more here: What is the correct JSON content type?

edited May 23 '17 at 11:48

Community

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answered Nov 22 '11 at 18:06

MilkyWayJoe

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score 0 · Answer 2 · answered Nov 22 '11 at 18:12

0

Why not get the JSON object in a callback? Check the success setting.

$.ajax({
     url: absPath + '/users/findUsers',
     type: 'POST',
     data: {contents: $('#messageTo').val()},
     dataType: 'json',
     success: function(data){
         var availableUsers = data;
         alert(typeof availableUsers);
     },
     async: false 
});

With the callback, you may do what ever you want with the object you got from the server.

answered Nov 22 '11 at 18:12

OnesimusUnbound

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my availableUsers is a global variable and I need it outside that anonymous function under the $.ajax({})! $.parseJSON helped the trick ;) – Nov 22 '11 at 18:14
@Commando: Then just remove the `var`. But honestly you should not use synchronous requests. They are not needed in most cases. – Felix Kling Nov 22 '11 at 18:41

JSON string evaluation with JavaScript, and getting it's value with JavaScript

2 Answers2