JS实现页面等高

function alignHeight(eleA,eleB,eleC){
//alert(eleA);
  if(!document.getElementById(eleA)){return false;}
  if(!document.getElementById(eleB)){return false;}
  if(!document.getElementById(eleC)){return false;}
 
  var heightA = document.getElementById(eleA).clientHeight;
  var heightB = document.getElementById(eleB).clientHeight;
  var heightC = document.getElementById(eleC).clientHeight;

  var height=new Array(heightA,heightB,heightC);
  var a=Math.max.apply(Math,height);
  console.log(a);
    document.getElementById(eleA).style.height = a + "px";
      document.getElementById(eleB).style.height = a + "px";
      document.getElementById(eleC).style.height = a + "px";
}
window.onload=function h(){
alignHeight("mainBox","subMainBox","sideBox");

};

//js数组求最大最小值可以这么写，不用自己写遍历比较

最大：Math.max.apply(Math,array);

最小:Math.min.apply(Math,array);