<!DOCTYPE html>
<html lang="zh-CN">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1, minimum-scale=1, user-scalable=no">
<title>3.2 通用适配实现</title>
<style>
* {
box-sizing: border-box;
padding: 0;
margin: 0;
}
.header-container {
width: 100%;
height: 2.5rem;
background-color: rgba(222, 24, 27, 0.9);
border-bottom: 1px solid #000;
}
</style>
<script>
(function () {
'use strict';
// dpr->scale = 1 / dpr
var docEl = document.documentElement,
viewportEl = document.querySelector('meta[name="viewport"]'),
dpr = window.devicePixelRatio || 1,
maxWidth = 540,
minWidth = 320;
dpr = dpr >= 3 ? 3 : (dpr >= 2 ? 2 : 1);
docEl.setAttribute('data-dpr', dpr);
docEl.setAttribute('max-width', maxWidth);
docEl.setAttribute('min-width', minWidth);
var scale = 1 / dpr,
content = 'width=device-width, initial-scale=' + scale + ', maximum-scale=' + scale + ', minimum-scale=' + scale + ', user-scalable=no';
if (viewportEl) {
viewportEl.setAttribute('content', content);
} else {
viewportEl = document.createElement('meta');
viewportEl.setAttribute('name', 'viewport');
viewportEl.setAttribute('content', content);
document.head.appendChild(viewportEl);
}
setRemUnit();
window.addEventListener('resize', setRemUnit);
function setRemUnit() {
var ratio = 18.75;
var viewWidth = docEl.getBoundingClientRect().width || window.innerWidth;
// console.log(viewWidth);
if (maxWidth && (viewWidth / dpr > maxWidth)) {
viewWidth = maxWidth * dpr;
} else if (minWidth && (viewWidth / dpr < minWidth)) {
viewWidth = minWidth * dpr;
}
docEl.style.fontSize = viewWidth / ratio + 'px';
}
})();
</script>
<!-- <script src="js/flexible.js"></script> -->
</head>
<body>
<header class="header-container"></header>
</body>
</html>