<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>无标题文档</title>
<meta name="viewport" content="initial-scale=1.0,user-scalable=no,maximum-scale=1,width=device-width" />
</head>
<body>
<script>
var throttle = function(fn,timeout ){
var timer;
return function(){
var self = this,
args = arguments;
clearTimeout( timer );
timer = setTimeout(function(){
fn.apply( self, args );
}, timeout );
};
};
var doc=document;
screenWd=doc.documentElement.clientWidth;
doc.getElementsByTagName("html")[0].style.fontSize=screenWd/10+'px';
// console.log(document.getElementsByTagName("html")[0].style.fontSize);
window.addEventListener("resize", throttle(function(){ //监听绑定
document.getElementsByTagName("html")[0].style.fontSize=document.documentElement.clientWidth/10+'px';
},150),false);
</script>
<style>
*{ margin:0; padding:0;}
html{ min-width:320px; font-size:62.5%;}
#header{ width:10rem; height:1.8rem; line-height:1.8rem;background:-webkit-linear-gradient(top,#333,#999); text-align:center; color:#fff;}
.warp{ width:10rem; margin:0 auto; height:300px;} /* 总共分20分 左边 10 间隙1 2隔间系2*/
.div1{ width:3rem;float:left;height:10rem;background:#eee}
.div2{ width:3rem; margin-left:0.5rem;float:left;height:11rem; background:#303}
.div3{ width:3rem; margin-left:0.5rem;float:left;height:8rem;background:#666}
#footer{ width:100%; height:1.8rem; line-height:1.8rem; background:#333; text-align:center; color:#fff; position:absolute; bottom:0; left:0;}
</style>
<header id="header">头部观察文字大小</header>
<div class="warp">
<div class="div1">left</div>
<div class="div2">中间</div>
<div class="div3">右侧eft</div>
</div>
<footer id="footer">底部</footer>
</body>
</html>
rem两个比较好的框架
淘宝Flexible https://github.com/amfe/lib-flexible
使用Flexible实现手淘H5页面的终端适配 https://github.com/amfe/article/issues/17
adaptive https://github.com/finance-sh/adaptive
网易的rem函数
<script type="text/javascript">
var Dpr = 1, uAgent = window.navigator.userAgent;
var isIOS = uAgent.match(/iphone/i);
var isYIXIN = uAgent.match(/yixin/i);
var is2345 = uAgent.match(/Mb2345/i);
var ishaosou = uAgent.match(/mso_app/i);
var isSogou = uAgent.match(/sogoumobilebrowser/ig);
var isLiebao = uAgent.match(/liebaofast/i);
var isGnbr = uAgent.match(/GNBR/i);
function resizeRoot(){
var wWidth = (screen.width > 0) ? (window.innerWidth >= screen.width || window.innerWidth == 0) ? screen.width : window.innerWidth : window.innerWidth, wDpr, wFsize;
var wHeight = (screen.height > 0) ? (window.innerHeight >= screen.height || window.innerHeight == 0) ? screen.height : window.innerHeight : window.innerHeight;
if (window.devicePixelRatio) {
wDpr = window.devicePixelRatio;
} else {
wDpr = isIOS ? wWidth > 818 ? 3 : wWidth > 480 ? 2 : 1 : 1;
}
if(isIOS) {
wWidth = screen.width;
wHeight = screen.height;
}
// if(window.orientation==90||window.orientation==-90){
// wWidth = wHeight;
// }else if((window.orientation==180||window.orientation==0)){
// }
if(wWidth > wHeight){
wWidth = wHeight;
}
wFsize = wWidth > 1080 ? 144 : wWidth / 7.5;
wFsize = wFsize > 32 ? wFsize : 32;
window.screenWidth_ = wWidth;
if(isYIXIN || is2345 || ishaosou || isSogou || isLiebao || isGnbr){//YIXIN 和 2345 这里有个刚调用系统浏览器时候的bug，需要一点延迟来获取
setTimeout(function(){
wWidth = (screen.width > 0) ? (window.innerWidth >= screen.width || window.innerWidth == 0) ? screen.width : window.innerWidth : window.innerWidth;
wHeight = (screen.height > 0) ? (window.innerHeight >= screen.height || window.innerHeight == 0) ? screen.height : window.innerHeight : window.innerHeight;
wFsize = wWidth > 1080 ? 144 : wWidth / 7.5;
wFsize = wFsize > 32 ? wFsize : 32;
// document.getElementsByTagName('html')[0].dataset.dpr = wDpr;
document.getElementsByTagName('html')[0].style.fontSize = wFsize + 'px';
document.getElementById("fixed").style.display="none";
},500);
}else{
// document.getElementsByTagName('html')[0].dataset.dpr = wDpr;
document.getElementsByTagName('html')[0].style.fontSize = wFsize + 'px';
document.getElementById("fixed").style.display="none";
}
// alert("fz="+wFsize+";dpr="+window.devicePixelRatio+";UA="+uAgent+";width="+wWidth+";sw="+screen.width+";wiw="+window.innerWidth+";wsw="+window.screen.width+window.screen.availWidth);
}
resizeRoot();
</script>
var adaptive = {};
(function (win, lib) {
var doc = win.document;
var docEl = doc.documentElement;
// 设备像素比
var devicePixelRatio = win.devicePixelRatio;
// 我们设置的布局视口与理想视口的像素比
var dpr = 1;
// viewport缩放值
var scale = 1;
// 设置viewport
function setViewport() {
// 判断IOS
var isIPhone = /iphone/gi.test(win.navigator.appVersion);
if (lib.scaleType === 2 && isIPhone || lib.scaleType === 3) {
dpr = devicePixelRatio;
}
// window对象上增加一个属性，提供对外的布局视口与理想视口的值
win.devicePixelRatioValue = dpr;
// viewport缩放值，布局视口缩放后刚好显示成理想视口的宽度，页面就不会过长或过短了
scale = 1 / dpr;
// 获取已有的viewport
var hasMetaEl = doc.querySelector('meta[name="viewport"]');
var metaStr = 'initial-scale=' + scale + ', maximum-scale=' + scale + ', minimum-scale=' + scale + ', user-scalable=no';
if (dpr === 1) {
metaStr = 'width=device-width, '.concat(metaStr);
}
if (!isIPhone && dpr !== 1) {
metaStr = metaStr.concat(', target-densitydpi=device-dpi');
}
// 如果有，改变之
if (hasMetaEl) {
hasMetaEl.setAttribute('content', metaStr);
}
// 如果没有，添加之
else {
var metaEl = doc.createElement('meta');
metaEl.setAttribute('name', 'viewport');
metaEl.setAttribute('content', metaStr);
if (docEl.firstElementChild) {
docEl.firstElementChild.appendChild(metaEl);
}
else {
var containDiv = doc.createElement('div');
containDiv.appendChild(metaEl);
docEl.appendChild(containDiv);
}
}
}
var newBase = 100;
lib.errDpr = 1;
function setRem() {
// 布局视口
// var layoutView = docEl.clientWidth; 也可以 获取布局视口的宽度
var layoutView;
if (lib.maxWidth) {
layoutView = Math.min(docEl.getBoundingClientRect().width, lib.maxWidth * dpr);
}
else {
layoutView = docEl.getBoundingClientRect().width;
}
// 为了计算方便，我们规定 1rem === 100px设计图像素，我们切图的时候就能快速转换
// 有人问，为什么不让1rem === 1px设计像素呢？
// 设计图一般是640或者750px
// 布局视口一般是320到1440
// 计算一个值，使layout的总宽度为 (desinWidth/100) rem
// 那么有计算公式：layoutView / newBase = desinWidth / 100
// newBase = 100 * layoutView / desinWidth
// newBase = 介于50到200之间
// 如果 1rem === 1px 设计像素，newBase就介于0.5到2之间，由于很多浏览器有最小12px限制，这个时候就不能自适应了
newBase = 100 * layoutView / lib.desinWidth * (lib.errDpr || 1);
docEl.style.fontSize = newBase + 'px';
// rem基准值改变后，手动reflow一下，避免旋转手机后页面自适应问题
doc.body&&(doc.body.style.fontSize = lib.baseFont / 100 + 'rem');
// 重新设置rem后的回调方法
lib.setRemCallback&&lib.setRemCallback();
lib.newBase = newBase;
}
var tid;
lib.desinWidth = 750;
lib.baseFont = 28;
// 局部刷新的时候部分chrome版本字体过大的问题
lib.reflow = function() {
docEl.clientWidth;
};
// 检查安卓下rem值是否显示正确
function checkRem() {
if (/android/ig.test(win.navigator.appVersion)) {
var hideDiv = document.createElement('p');
hideDiv.style.height = '1px';
hideDiv.style.width = '2.5rem';
hideDiv.style.visibility = 'hidden';
document.body.appendChild(hideDiv);
var now = hideDiv.offsetWidth;
var right = lib.newBase * 2.5;
if (Math.abs(right / now - 1) > 0.05) {
lib.errDpr = right / now;
setRem();
}
document.body.removeChild(hideDiv);
}
}
lib.init = function () {
// resize的时候重新设置rem基准值
// 触发orientationchange 事件时也会触发resize，故不需要再添加此事件了
win.addEventListener('resize', function () {
clearTimeout(tid);
tid = setTimeout(setRem, 300);
}, false);
// 浏览器缓存中读取时也需要重新设置rem基准值
win.addEventListener('pageshow', function (e) {
if (e.persisted) {
clearTimeout(tid);
tid = setTimeout(setRem, 300);
}
}, false);
// 设置body上的字体大小
if (doc.readyState === 'complete') {
doc.body.style.fontSize = lib.baseFont / 100 + 'rem';
checkRem();
}
else {
doc.addEventListener('DOMContentLoaded', function (e) {
doc.body.style.fontSize = lib.baseFont / 100 + 'rem';
checkRem();
}, false);
}
setViewport();
// 设置rem值
setRem();
// html节点设置布局视口与理想视口的像素比
docEl.setAttribute('data-dpr', dpr);
};
// 有些html元素只能以px为单位，所以需要提供一个接口，把rem单位换算成px
lib.remToPx = function (remValue) {
return remValue * newBase;
};
})(window, adaptive);
if (typeof module != 'undefined' && module.exports) {
module.exports = adaptive;
} else if (typeof define == 'function' && define.amd) {
define(function() {
return adaptive;
});
} else {
window.adaptive = adaptive;
}
<script>
// 设计图宽度
window['adaptive'].desinWidth = 640;
// body 字体大小 会将body字体大小设置为 baseFont / 100 + 'rem' 750的设计图一般设置为28,640的设计图一般设置为24
window['adaptive'].baseFont = 24;
/*
// 显示最大宽度 可选
window['adaptive'].maxWidth = 480;
// rem值改变后执行方法 可选
window['adaptive'].setRemCallback = function () {
alert(1)
}
// scaleType 1:iphone andriod下viewport均无缩放 2:iphone下viewport有缩放,andriod没有 3:iphone andriod下viewport均有缩放; 默认值为1
window['adaptive'].scaleType = 1;
*/
// 初始化
window['adaptive'].init();
</script>