String.prototype.trim = function() { return this.replace(/^\s*|\s*$/g, ""); };

String.prototype.checkEmail = function() {
	var re = /^([a-zA-Z0-9_.-])+@(([a-zA-Z0-9-])+.)+([a-zA-Z0-9]{2,4})+$/;
	return this.match(re);
}