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

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

String.prototype.checkDNI = function() {
	var n = this.substr(0, this.length-1);
	var l = this.substr(this.length-1,1);
	n = n % 23;
	var llist = 'TRWAGMYFPDXBNJZSQVHLCKET';
	var character = llist.substring(n, n + 1);
	if (character != l) {
		return false;
	} else {
		return true;
	}
};