rem
// 设计稿宽度 : 750 ( 2倍图 )
// 缩放比例 : 100 ( 1rem === 100px )
(function (win, doc) {
function setRootFontSize() {
let docWidth = doc.documentElement.getBoundingClientRect().width
doc.documentElement.style.fontSize = docWidth / 750 * 100 + 'px'
}
setRootFontSize()
win.addEventListener('resize', setRootFontSize, !1)
})(window, document)