We do it this way...
String.prototype.getValueByKey = function (k) {
var p = new RegExp('\\b' + k + '\\b', 'gi');
return this.search(p) != -1 ? decodeURIComponent(this.substr(this.search(p) + k.length + 1).substr(0, this.substr(this.search(p) + k.length + 1).search(/(&|;|$)/))) : "";
};