DOM编程艺术推荐的addLoadEvent和insertAfter

addLoadEvent.js

function addLoadEvent(func){
    var oldonLoad = window.onload;
    if(typeof window.onload!='function'){
            window.onload = func;
    }
    else{
        window.onload = function(){
            oldonload();
            func();
        }
    }
}

insertAfter.js

function insertAfter(newElement,targetElement) {
  var parent = targetElement.parentNode;
  if (parent.lastChild == targetElement) {
    parent.appendChild(newElement);
  } else {
    parent.insertBefore(newElement,targetElement.nextSibling);
  }
}

/**
 * [addClass 追加一个新class]
 * @param {[type]} element [description]
 * @param {[type]} value   [description]
 */
function addClass(element, value) {
	if (!element.className) {
		element.className = value;
	} else {
		newClassName = element.className;
		newclassName = " ";
		newclassName += value;
		element.className = newclassName;
	}
}