Copy of http://unixpapa.com/js/QueryString.js 7/29/2012

QueryString.js

// This is public domain code written in 2011 by Jan Wolter and distributed
// for free at http://unixpapa.com/js/querystring.html
//
// Query String Parser
//
//    qs= new QueryString()
//    qs= new QueryString(string)
//
//        Create a query string object based on the given query string. If
//        no string is given, we use the one from the current page by default.
//
//    qs.value(key)
//
//        Return a value for the named key.  If the key was not defined,
//        it will return undefined. If the key was multiply defined it will
//        return the last value set. If it was defined without a value, it
//        will return an empty string.
//
//   qs.values(key)
//
//        Return an array of values for the named key. If the key was not
//        defined, an empty array will be returned. If the key was multiply
//        defined, the values will be given in the order they appeared on
//        in the query string.
//
//   qs.keys()
//
//        Return an array of unique keys in the query string.  The order will
//        not necessarily be the same as in the original query, and repeated
//        keys will only be listed once.
//
//    QueryString.decode(string)
//
//        This static method is an error tolerant version of the builtin
//        function decodeURIComponent(), modified to also change pluses into
//        spaces, so that it is suitable for query string decoding. You
//        shouldn't usually need to call this yourself as the value(),
//        values(), and keys() methods already decode everything they return.
//
// Note: W3C recommends that ; be accepted as an alternative to & for
// separating query string fields. To support that, simply insert a semicolon
// immediately after each ampersand in the regular expression in the first
// function below.

function QueryString(qs)
{
    this.dict= {};

    // If no query string  was passed in use the one from the current page
    if (!qs) qs= location.search;

    // Delete leading question mark, if there is one
    if (qs.charAt(0) == '?') qs= qs.substring(1);

    // Parse it
    var re= /([^=&]+)(=([^&]*))?/g;
    while (match= re.exec(qs))
    {
	var key= decodeURIComponent(match[1].replace(/\+/g,' '));
	var value= match[3] ? QueryString.decode(match[3]) : '';
	if (this.dict[key])
	    this.dict[key].push(value);
	else
	    this.dict[key]= [value];
    }
}

QueryString.decode= function(s)
{
    s= s.replace(/\+/g,' ');
    s= s.replace(/%([EF][0-9A-F])%([89AB][0-9A-F])%([89AB][0-9A-F])/g,
	function(code,hex1,hex2,hex3)
	{
	    var n1= parseInt(hex1,16)-0xE0;
	    var n2= parseInt(hex2,16)-0x80;
	    if (n1 == 0 && n2 < 32) return code;
	    var n3= parseInt(hex3,16)-0x80;
	    var n= (n1<<12) + (n2<<6) + n3;
	    if (n > 0xFFFF) return code;
	    return String.fromCharCode(n);
	});
    s= s.replace(/%([CD][0-9A-F])%([89AB][0-9A-F])/g,
	function(code,hex1,hex2)
	{
	    var n1= parseInt(hex1,16)-0xC0;
	    if (n1 < 2) return code;
	    var n2= parseInt(hex2,16)-0x80;
	    return String.fromCharCode((n1<<6)+n2);
	});
    s= s.replace(/%([0-7][0-9A-F])/g,
	function(code,hex)
	{
	    return String.fromCharCode(parseInt(hex,16));
	});
    return s;
};

QueryString.prototype.value= function (key)
{
    var a= this.dict[key];
    return a ? a[a.length-1] : undefined;
};

QueryString.prototype.values= function (key)
{
    var a= this.dict[key];
    return a ? a : [];
};

QueryString.prototype.keys= function ()
{
    var a= [];
    for (var key in this.dict)
	a.push(key);
    return a;
};