CORS problem code example

Example 1: allow cross origin

Access-Control-Allow-Origin: *
Access-Control-Allow-Origin: <origin>
Access-Control-Allow-Origin: null

Example 2: javascript cors error

$.ajax({
            headers: { "Accept": "application/json"},
            type: 'GET',
            url: 'http://cl.ly/2wr4',
            crossDomain: true,
            beforeSend: function(xhr){
                xhr.withCredentials = true;
          },
            success: function(data, textStatus, request){
                console.log(data);
            }
 });