load - jQuery how to build a link with json?, error -

i have this:

    $.get('xxx.php', { username: username },     function(data){         var get_back = data;         alert(get_back); }); 

this return get_back=12345

and i'm trying build this:

url: "http://www.test.com/users/" + get_back, 

the result http://www.test.com/users/12345

for reason doesn't want work. if hard-code 12345 in link work. i've tryed url: "http://www.test.com/users/" + get_back + "", , url: 'http://www.test.com/users/' + get_back,

any ideas?

edit:

$.ajax({ type: "post", data: json.stringify(formdata), datatype: "json", url: "http://www.test.com/users/" + get_back + "", success: function(t){    alert(t);  } }); 

that because get_back might in scope of else. either can call get_back before $.get call , global or can put on object this:

var = {    get_back: null,    init: function(username){       var self = this;       $.get('xxx.php', { username: username },           function(data){               self.get_back = data;               self.runajax(); //run ajax when get_back instantiated           }       });     },    runajax: function(){       var self = this;       $.ajax({          type: "post",          data: json.stringify(formdata),          datatype: "json",          url: "http://www.test.com/users/" + self.get_back + "",          success: function(t){    alert(t);  }          });    } }  //to use it: get.init(username); //to use get_back alert(get.get_back); 

updated ajax

you might have add formdata object somehow, dont know created