if (i%4 ==0 ) 逻辑的魅力 在于 这里

<div class="course_height">

</div>
  <script src="js/jquery.min.js"></script>
  <script>
var i=0;
var s1 = "<ul class='intelliGence'>";
var s3 = "</ul>";
var shtml = "";
 for(i=0;i<20;i++){
   var s2='<li>'+i+'</li>';
      if(i%4 == 0){
        shtml += s1;
      }
      shtml += s2;
      if((i+1)%4 == 0){
        shtml += s3;
      }
 }
	   shtml += s3;
     var recbody = $(".course_height");
    recbody.text("");
    recbody.append(shtml);
  </script>