Get query string value using JavaScript

Here is the JavaScript function getQuerystring which finds the key form query string and returns the value.

/*
* <summary>
* Get the querystring value
* </summary>
* <param name="key">A string contains the querystring key</param>
* <param name="defaultVal">Object which get returns when there is not key</param>
**/
function getQuerystring(key, defaultVal) {
    if (defaultVal == null) {
        defaultVal = "";
    }
    key = key.replace(/[\[]/, "\\\[").replace(/[\]]/, "\\\]");
    var regex = new RegExp("[\\?&]" + key + "=([^&#]*)");
    var qs = regex.exec(window.location.href);
    if (qs == null) {
        return defaultVal;
    }
    else {
        return qs[1];
    } 
}