移动开发，Webapp 淘宝手机 rem 布局

(function (doc, win) {
var docEl = doc.documentElement,
resizeEvt ="orientationchange"in window ?"orientationchange":"resize",
recalc = function () {
var clientWidth = docEl.clientWidth;
if (!clientWidth) return;
if (clientWidth<640){
docEl.style.fontSize = 12 * (clientWidth / 320) +"px";
console.log(12 * (clientWidth / 320) +"px");
}else{
//docEl.style.fontSize ="12px";
docEl.style.fontSize = 12 * ( 640 / 320) +"px";
}
};

if (!doc.addEventListener) return;
win.addEventListener(resizeEvt, recalc, false);
doc.addEventListener('DOMContentLoaded', recalc, false);})(document, window);