移动端 rem.js动态控制 适配

直接上代码： 

(function remYS(doc, win) {
            var docEl = doc.documentElement,
             resizeEvt = 'orientationchange' in win? 'orientationchange' : 'resize',
             recalc = function () {
               var clientWidth = docEl.clientWidth;
               if (clientWidth === undefined) return;
               docEl.style.fontSize = 16 * (clientWidth / 320) + 'px';
             };
           if (doc.addEventListener === undefined) return;
          win.addEventListener(resizeEvt, recalc, false);
           doc.addEventListener('DOMContentLoaded', recalc, false)
        })(document, window)