;(function(win, lib) {
???var doc = win.document;
???var docEl = doc.documentElement;
???var metaEl = doc.querySelector(‘meta[name="viewport"]‘);
???var flexibleEl = doc.querySelector(‘meta[name="flexible"]‘);
???var dpr = 0;
???var scale = 0;
???var tid;
???var flexible = lib.flexible || (lib.flexible = {});
???
???if (metaEl) {
???????console.warn(‘将根据已有的meta标签来设置缩放比例‘);
???????var match = metaEl.getAttribute(‘content‘).match(/initial\-scale=([\d\.]+)/);
???????if (match) {
???????????scale = parseFloat(match[1]);
???????????dpr = parseInt(1 / scale);
???????}
???} else if (flexibleEl) {
???????var content = flexibleEl.getAttribute(‘content‘);
???????if (content) {
???????????var initialDpr = content.match(/initial\-dpr=([\d\.]+)/);
???????????var maximumDpr = content.match(/maximum\-dpr=([\d\.]+)/);
???????????if (initialDpr) {
???????????????dpr = parseFloat(initialDpr[1]);
???????????????scale = parseFloat((1 / dpr).toFixed(2)); ???
???????????}
???????????if (maximumDpr) {
???????????????dpr = parseFloat(maximumDpr[1]);
???????????????scale = parseFloat((1 / dpr).toFixed(2)); ???
???????????}
???????}
???}
???if (!dpr && !scale) {
???????var isAndroid = win.navigator.appVersion.match(/android/gi);
???????var isIPhone = win.navigator.appVersion.match(/iphone/gi);
???????var devicePixelRatio = win.devicePixelRatio;
???????if (isIPhone) {
???????????// iOS下，对于2和3的屏，用2倍的方案，其余的用1倍方案
???????????if (devicePixelRatio >= 3 && (!dpr || dpr >= 3)) { ???????????????
???????????????dpr = 3;
???????????} else if (devicePixelRatio >= 2 && (!dpr || dpr >= 2)){
???????????????dpr = 2;
???????????} else {
???????????????dpr = 1;
???????????}
???????} else {
???????????// 其他设备下，仍旧使用1倍的方案
???????????dpr = 1;
???????}
???????scale = 1 / dpr;
???}
???docEl.setAttribute(‘data-dpr‘, dpr);
???if (!metaEl) {
???????metaEl = doc.createElement(‘meta‘);
???????metaEl.setAttribute(‘name‘, ‘viewport‘);
???????metaEl.setAttribute(‘content‘, ‘initial-scale=‘ + scale + ‘, maximum-scale=‘ + scale + ‘, minimum-scale=‘ + scale + ‘, user-scalable=no‘);
???????if (docEl.firstElementChild) {
???????????docEl.firstElementChild.appendChild(metaEl);
???????} else {
???????????var wrap = doc.createElement(‘div‘);
???????????wrap.appendChild(metaEl);
???????????doc.write(wrap.innerHTML);
???????}
???}
???function refreshRem(){
???????var width = docEl.getBoundingClientRect().width;
???????if (width / dpr > 540) {
???????????width = 540 * dpr;
???????}
???????var rem = width / 10;
???????docEl.style.fontSize = rem + ‘px‘;
???????flexible.rem = win.rem = rem;
???}
???win.addEventListener(‘resize‘, function() {
???????clearTimeout(tid);
???????tid = setTimeout(refreshRem, 300);
???}, false);
???win.addEventListener(‘pageshow‘, function(e) {
???????if (e.persisted) {
???????????clearTimeout(tid);
???????????tid = setTimeout(refreshRem, 300);
???????}
???}, false);
???if (doc.readyState === ‘complete‘) {
???????doc.body.style.fontSize = 12 * dpr + ‘px‘;
???} else {
???????doc.addEventListener(‘DOMContentLoaded‘, function(e) {
???????????doc.body.style.fontSize = 12 * dpr + ‘px‘;
???????}, false);
???}
???
???refreshRem();
???flexible.dpr = win.dpr = dpr;
???flexible.refreshRem = refreshRem;
???flexible.rem2px = function(d) {
???????var val = parseFloat(d) * this.rem;
???????if (typeof d === ‘string‘ && d.match(/rem$/)) {
???????????val += ‘px‘;
???????}
???????return val;
???}
???flexible.px2rem = function(d) {
???????var val = parseFloat(d) / this.rem;
???????if (typeof d === ‘string‘ && d.match(/px$/)) {
???????????val += ‘rem‘;
???????}
???????return val;
???}
})(window, window[‘lib‘] || (window[‘lib‘] = {}));
这段代码所做的主要事情就是把
1rem的大小定义为屏幕宽度的十分之一
flexible.js
原文地址：https://www.cnblogs.com/mingweiyard/p/9025213.html