JS封装通过className获取元素的函数示例

<div id="box">
  <div class="star"></div>
  <div class="star"></div>
  <div class="app"></div>
  <p class="star"></p>
  <p class="ar"></p>
</div>

function getByClass(oparent,sClass){
  var aEle=oparent.getElementsByTagName("");
  var aResult=[];
  var i;
  for(i=0;i<aEle.length;i++){
    if(aEle[i].className==sClass){
      aResult.push(aEle[i]);
    }
  }
  return aResult;
};
window.onload=function(){
  var box=document.getElementById("box");
  var star=getByClass(box,"star");
};