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");
};