;(function(win,doc){
   function changeSize(){
       doc.documentElement.style.fontSize=50*doc.documentElement.clientWidth/320+'px'
   }////50是可變的
   changeSize();
   window.addEventListener('resize',changeSize,false)
})(window,document);

!(function(doc, win) {
   var docEle = doc.documentElement,
       evt = "onorientationchange"
 
 in window ? "orientationchange" : "resize",
       fn = function() {
           var width = docEle.clientWidth;
           width && (docEle.style.fontSize = 50 * (width / 320) + "px");
       }; //50是可變的

   win.addEventListener(evt, fn, false);
   doc.addEventListener("DOMContentLoaded", fn, false
 
);

}(document, window));