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>