function alignHeight(eleA,eleB){
  if(!document.getElementById(eleA)){return false;}
  if(!document.getElementById(eleB)){return false;}
  var heightA = document.getElementById(eleA).clientHeight;
  var heightB = document.getElementById(eleB).clientHeight;
  if(heightA > heightB){
    document.getElementById(eleB).style.height = heightA + "px";
    document.getElementById(eleA).style.height = heightA + "px";
  }else{
    document.getElementById(eleA).style.height = heightB + "px";
    document.getElementById(eleB).style.height = heightB + "px";
  }
}
window.onload = 
function z_align(){
  alignHeight("Nleft","Nright"); 
  alignHeight("bb1","bb2");//只需将需要对齐的两个模块的id写在此处即可。
//alignHeight("AAA","BBB") 可依此连续多组。
}