jquery的each和JS的for比较

推荐减法的for

jsperf地址:https://jsperf.com/zlq463947

<script src="//ajax.googleapis.com/ajax/libs/jquery/3.1.1/jquery.min.js"></script>
<script src="//cdnjs.cloudflare.com/ajax/libs/underscore.js/1.8.3/underscore-min.js"></script>

<script>
  var pi = Math.PI
  var a = new Array(1000000),
      e;
</script>