json parse string
var jsonPerson = '{"first_name":"billy", "age":23}';
var personObject = JSON.parse(jsonPerson); //parse json string into JS object
Grepper
var jsonPerson = '{"first_name":"billy", "age":23}';
var personObject = JSON.parse(jsonPerson); //parse json string into JS object var str = '[{"UserName":"xxx","Rolename":"yyy"}]'; // your response in a string
var parsed = JSON.parse(str); // an *array* that contains the user
var user = parsed[0]; // a simple user
console.log(user.UserName); // you'll get xxx
console.log(user.Rolename); // you'll get yyy