Parse Query String in JavaScript. Demo: http://jsfiddle.net/nicz/hyDKE/

parse-query-string.js

/**
 * Convert a URL or just the query part of a URL to an
 * object with all keys and values.
 * Usage examples:
 *   // Get "GET" parameters from current request as object:
 *   var parameters = parseQueryString(window.location.search);
 */
function parseQueryString(query) {
        var obj = {},
            qPos = query.indexOf("?"),
	    tokens = query.substr(qPos + 1).split('&'),
	    i = tokens.length - 1;
	if (qPos !== -1 || query.indexOf("=") !== -1) {
		for (; i >= 0; i--) {
			var s = tokens[i].split('=');
			obj[unescape(s[0])] = s.hasOwnProperty(1) ? unescape(s[1]) : null;
		};
	}
	return obj;
}