Storing JSON Value in javascript Array

I am using JSON value to store in javascript array.

My JSON value :

"Users":[{"user_name":"User 1","id":1,"image_url":"/photos/list/missing.png","level":1,"position":{"name":"User ABC","description":"desc"}}]

I'm getting response in alert same as above. Code:

alert("Response : " + $.toJSON(res["Users"]));

O/P : Response : [{"user_name":"User 1","id":1,"image_url":"/photos/list/missing.png","level":1,"position":{"name":"User ABC","description":"desc"}}]

Storing this value as Code:

tempJSON = $.toJSON(res["Users"]);

alert("JSON Array : " + tempJSON.length); alert("Name : " + tempJSON[0]. user_name);

O/P : JSON Array : 132 -> No. of characters. Name : Undefined. -> Because it can't find value for "user_name"

If I'm Storing this value as Simple String. Code:

tempJSON = [{"user_name":"User 1","id":1,"image_url":"/photos/list/missing.png","level":1,"position":{"name":"User ABC","description":"desc"}}];

alert("JSON Array : " + tempJSON.length); alert("Name : " + tempJSON[0]. user_name);

Then Getting Exactly,

O/P :

JSON Array : 1 -> No. of Array.

Name : User 1

I don't getting what's going on. Please tell me any solution.

Thanks in advance.