使用flexible js配合rem实现在不同宽度的设备中，网页元素尺寸等比缩放效果
lflexible.js是手淘开发出的一个用来适配移动端的js框架。
核心原理就是根据不同的视口宽度给网页中html根节点设置不同的font-size<script src="./js/flexible.js"></script>
(function flexible (window, document) {var docEl = document.documentElementvar dpr = window.devicePixelRatio || 1// adjust body font sizefunction setBodyFontSize () {if (document.body) {document.body.style.fontSize = (12 * dpr) + 'px'}else {document.addEventListener('DOMContentLoaded', setBodyFontSize)}}setBodyFontSize();// set 1rem = viewWidth / 10function setRemUnit () {var rem = docEl.clientWidth / 10docEl.style.fontSize = rem + 'px'}setRemUnit()// reset rem unit on page resizewindow.addEventListener('resize', setRemUnit)window.addEventListener('pageshow', function (e) {if (e.persisted) {setRemUnit()}})// detect 0.5px supportsif (dpr >= 2) {var fakeBody = document.createElement('body')var testElement = document.createElement('div')testElement.style.border = '.5px solid transparent'fakeBody.appendChild(testElement)docEl.appendChild(fakeBody)if (testElement.offsetHeight === 1) {docEl.classList.add('hairlines')}docEl.removeChild(fakeBody)}
}(window, document))