Return a query string from url

gistfile1.txt

var QueryString = function ()
{
  // This function is anonymous, is executed immediately and 
  // the return value is assigned to QueryString!
  var query_string = {};
  var query = window.location.search.substring(1);
  var vars = query.split("&");
  
  for (var i=0;i<vars.length;i++)
  {
	var pair = vars[i].split("=");
	
	// If first entry with this name
	if (typeof query_string[pair[0]] === "undefined")
	{
	  query_string[pair[0]] = decodeURIComponent(pair[1]);
		// If second entry with this name
	}
	else if(typeof query_string[pair[0]] === "string")
	{
	  var arr = [ query_string[pair[0]],decodeURIComponent(pair[1]) ];
	  query_string[pair[0]] = arr;
		// If third or later entry with this name
	}
	else
	{
	  query_string[pair[0]].push(decodeURIComponent(pair[1]));
	}
  } 
	return query_string;
}();
//http://localhost/client/index.php?&id=1
var _hash = QueryString.id;

//returns 1