deserialize JSON to JAVASCRIPT object

i have a question to deserialize JSON text to an javascript object, i test jquery and yui library, i have this class:

function Identifier(name, contextId) {
    this.name = name;
    this.contextId = contextId;
}

Identifier.prototype.setName = function(name) {
    this.name = name;
}

Identifier.prototype.getName = function() {
    return this.name;
}

Identifier.prototype.setContextId = function(contexId) {
    this.contextId= contexId;
}

Identifier.prototype.getContextId = function() {
    return this.contextId;
}

and i have this JSON:

{
"Identifier": { 
   "name":"uno",
   "contextId":"dos"}
}

I want to the parse create an Identifier object, my problem is that this sentences:

var obj = jQuery.parseJSON('{"Identifier": { "name":"uno","contextId":"dos"}}');

or

var obj2 = JSON.parse('{"Identifier": { "name":"uno","contextId":"dos"}}');

Dont work, the var obj and obj2 aren't an Identifier object, how can i parse this? Thanks

This question is not the duplicate, because it was made 5 years before than the question that Michael marks as duplicated