var rem=(function(doc, win) {
var docEl = doc.documentElement,//擷取整個文檔元素
resizeEvt = 'orientationchange' in window ? 'orientationchange' : 'resize',//相容safari和其他浏覽器
recalc = function() {
var hWidth = docEl.getBoundingClientRect().width;//擷取整個螢幕的寬度
docEl.style.fontSize = hWidth / 15 + 'px';
};
if (!doc.addEventListener) return;
win.addEventListener(resizeEvt, recalc, false);
doc.addEventListener('DOMContentLoaded', recalc, false);
})(document, window);