JavaScript で addClass / removeClass - Qiita

Element.prototype.hasClass = function(className){ var classArray = this.className.split(' '); return classArray.indexOf(className) >= 0; } Element.prototype.addClass = function(className){ if(!this.hasClass(className)){ var classArray = this.className.split(' '); classArray.push(className); this.className = classArray.join(' '); } return this; } Element.prototype.removeClass = function(className){