一个简单的移动端案例，模拟不同设备下逻辑分辨率不同，宽高自适应
正常打开整体布局
打开 f12 （ctrl + shift + M）或者点击左上角图标,将其模拟为移动端设备
在移动设备iPhone6/7/8，逻辑分辨率375的整体布局
其banner图尺寸
现在切换设备为iPad，逻辑分辨率为768，此设备下banner图尺寸自适应
再切换设备为iPhone 14 Pro Max，逻辑分辨率为430，此设备下banner图尺寸自适应
源码
HTML（index.html）代码
<!DOCTYPE html>
<html lang="en">
<head><meta charset="UTF-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><title>极速问诊</title><link rel="stylesheet" href="./iconfont/iconfont.css"><link rel="stylesheet" href="./css/index.css">
</head>
<body><!-- 头部区域 --><header><a href="#" class="back"><span class="iconfont icon-jiantou3"></span></a><h3>极速问诊</h3><a href="#" class="note">问诊记录</a></header><!-- banner区域 --><div class="banner"><img src="./assets/docter.jpg" alt=""><p><span>20s</span> 快速匹配专业医生</p></div><!-- 问诊类型 --><div class="type"><ul><li><a href="#"><span class="iconfont icon-yisheng"></span><div class="txt"><h4>三甲图文问诊</h4><p>三甲主治及以上级别医生</p></div><span class="iconfont icon-jiantou21"></span></a></li><li><a href="#"><span class="iconfont icon-xinxi1"></span><div class="txt"><h4>普通图文问诊</h4><p>二甲主治及以上级别医生</p></div><span class="iconfont icon-jiantou21"></span></a></li></ul></div><!-- 引入flexible.js移动端布局js --><script src="./js/flexible.js"></script>
</body>
</html>CSS样式（index.css）代码：
*,
::after,
::before {box-sizing: border-box;
}
body,
ul,
ol,
p,
h1,
h2,
h3,
h4,
h5,
h6 {margin: 0;padding: 0;
}
body {font-family: -apple-system, BlinkMacSystemFont, PingFangSC-Regular, "PingFang SC", "Microsoft YaHei", "Helvetica Neue", Helvetica, Arial, sans-serif;font-size: 14px;color: #333;
}
a {color: #333;text-decoration: none;-webkit-tap-highlight-color: regb(0, 0, 0, 0);
}
ul {list-style-type: none;
}
li {list-style: none;
}
img {vertical-align: bottom;
}
header {display: flex;justify-content: space-between;padding: 0 0.4rem;height: 1.17333333rem;line-height: 1.17333333rem;
}
header .icon-jiantou3 {font-size: 0.48rem;
}
header h3 {font-size: 0.45333333rem;
}
header .note {font-size: 0.4rem;color: #2cb2a5;
}
.banner {margin-top: 0.8rem;margin-bottom: 0.90666667rem;text-align: center;
}
.banner img {margin-bottom: 0.48rem;width: 6.4rem;height: 5.49333333rem;
}
.banner p {font-size: 0.42666667rem;
}
.banner p span {color: #16c2a3;
}
.type {padding: 0 0.4rem;
}
.type li {margin-bottom: 0.4rem;padding: 0 0.4rem;height: 2.08rem;border: 0.5px solid #ededed;border-radius: 0.10666667rem;
}
.type a {display: flex;align-items: center;height: 2.08rem;
}
.type a .icon-yisheng,
.type a .icon-xinxi1 {margin-right: 0.37333333rem;width: 1.06666667rem;height: 1.06666667rem;border-radius: 50%;line-height: 1.06666667rem;text-align: center;font-size: 0.64rem;color: #faf5f5;
}
.type a .icon-yisheng {background-color: #16c2a3;background-image: linear-gradient(to right bottom, #a3eddf, #41c2aa);
}
.type a .icon-xinxi1 {background-color: aqua;background-image: linear-gradient(to right bottom, #97c4f3, #6c8dde);
}
.type a .txt {flex: 1;
}
.type a .txt h4 {margin-bottom: 0.13333333rem;font-size: 0.42666667rem;color: #3c3e42;line-height: 0.64rem;
}
.type a .txt p {font-size: 0.34666667rem;color: #848484;line-height: 0.53333333rem;
}
.type a .icon-jiantou21 {font-size: 0.42666667rem;
}JS（flexible.js）代码：
(function flexible(window, document) {//获取html根目录var docEl = document.documentElement//dpr 物理像素比var dpr = window.devicePixelRatio || 1// adjust body font size 设置body字体大小function setBodyFontSize() {if (document.body) {document.body.style.fontSize = (12 * dpr) + 'px'} else {//如果页面没有body 这个元素，则只用DOMContentLoaded 监听，等待 DOM 元素加载完毕document.addEventListener('DOMContentLoaded', setBodyFontSize)}}setBodyFontSize();// set 1rem = viewWidth / 10 设置html 元素字体大小function setRemUnit() {var rem = docEl.clientWidth / 10docEl.style.fontSize = rem + 'px'}setRemUnit()// reset rem unit on page resize 当页面尺寸大小发生改变时，重新设置一下rem大小。window.addEventListener('resize', setRemUnit)//pageshow 是我们重新加载页面触发的事件window.addEventListener('pageshow', function(e) {//e.persisted 返回的是 true 就是如果这个页面从缓存中获取过来，也要重新设置rem大小if (e.persisted) {setRemUnit()}})// detect 0.5px supports 解决移动端浏览器支持0.5像素if (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))