Element.prototype.hasClassName = function (a) {
return new RegExp("(?:^|\\s+)" + a + "(?:\\s+|$)").test(this.className);
};

Element.prototype.addClassName = function (a) {
if (!this.hasClassName(a)) {
this.className = [this.className, a].join(" ");
} };

Element.prototype.removeClassName = function (b) {
if (this.hasClassName(b)) {
var a = this.className; this.className = a.replace(new RegExp("(?:^|\\s+)" + b + "(?:\\s+|$)", "g"), " ");
} };

Element.prototype.toggleClassName = function (a) {
this[this.hasClassName(a) ? "removeClassName" : "addClassName"](a);
};
example