Get querystring value in javascript [using html5]

function Get_Userid() {
            var qsarr = new Array();
            var qs = location.search.substring(1);
            var singleqs = new Array();
            var str = "";
            qsarr = qs.split('&');
            for (i = 0; i < qsarr.length; i++) {
                singleqs = qsarr[i].split('=');
                //                str += 'Query String Name : <span style="color:#ff0000;">' + singleqs[0] +
                //            '</span> and its value is : <span style="color:#ff0000;">' + singleqs[1] + '</span><br />';
            }
            document.getElementById('hidden_Username').value = singleqs[1];
            alert(document.getElementById('hidden_Username').value);
        }