classNameやcssTextでstyleの操作を減らす

 element.style.color = "red";
 element.style.fontSize = "25px";

 .active {
     color: red;
     fontsize: 25px;
 }
 
 element.className = "active";

 element.style.cssText = "color: red; fontSize: 25px;"

出典

http://www.slideshare.net/nzakas/writing-efficient-javascript