原生js设置rem

setFontSize: function (doc, win) {
var docEl = doc.documentElement
var resizeEvt = 'orientationchange' in window ? 'orientationchange' : 'resize'
var reCaculate = function () {
var clientWidth = docEl.clientWidth
if (!clientWidth) return
docEl.style.fontSize = 100 * (clientWidth / 750) + 'px'
}
if (!doc.addEventListener) return
win.addEventListener(resizeEvt, reCaculate, false)
doc.addEventListener('DOMContentLoaded', reCaculate, false)
},