Reading Querystring value using JavaScript

The following function can be used to read the value of given key from querystring.

/* function to read value of the given key
, x, from querystring */
function GetQStringVal(x) {

    var a = location.search.substring(1); 
    var b = a.split("&");

    for (var i = 0; i < b.length; i++) {

        var c = b[i].split("=");
        if (c[0].toLowerCase() == x.toLowerCase()) 
        { 
           return c[1]; 
        }
    }
    return "";
}