手机端转换rem适应

 <script>
  (function() {
   var changeRem = function() {
    document.getElementsByTagName('html')[0].style.fontSize = document.documentElement.clientWidth / 20 + 'px';
   };
   changeRem();
   var t;
   window.addEventListener('resize', function() {
    clearTimeout(t);
    t = setTimeout(changeRem, 300);
   }, false);
   window.addEventListener('pageshow', function(e) {
    if (e.persisted) {
     clearTimeout(t);
     t = setTimeout(changeRem, 300);
    }
   }, false);
  }());
 </script>