3-4请老师检查下代码，谢谢

来源：3-4 自由编程

不厌_

2021-07-29 23:37:28

html相关代码：

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <title>Document</title>
    <style>
        * {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
        }

        img {
            vertical-align: top;
            border: none;
            width: 100%;
        }

        [data-dpr='2'] body,
        [data-dpr='2'] a,
        [data-dpr='2'] input {
            font-size: 24px;
        }

        [data-dpr='3'] body,
        [data-dpr='3'] a,
        [data-dpr='3'] input {
            font-size: 36px;
        }

        .header {
            width: 100%;
            height: 2.5rem;
            background-color: rgb(189, 183, 184);
            display: flex;
            position: fixed;
            top: 0;
            left: 0;
            z-index: 999;
        }

        .header-left,
        .header-right {
            display: flex;
            height: 100%;
            flex: 1;
            align-items: center;
        }

        .header-left {
            justify-content: flex-start;
        }

        .header-right {
            justify-content: flex-end;
        }

        .header-left .logo {
            padding-left: 1rem;
            display: flex;
            width: 7rem;
            justify-content: center;
            align-items: center;
            cursor: pointer;
        }

        .header-right .download-btn {
            margin-right: 1rem;
            background-color: rgb(233, 193, 199);
            width: 3.25rem;
            height: 1.25rem;
            color: black;
            border-radius: .75rem;
            display: flex;
            justify-content: center;
            align-items: center;
        }
    </style>
</head>

<body>
    <header class="header">
        <div class="header-left">
            <div class="logo">
                <img src="./img/logo.png" alt="">
            </div>
        </div>
        <div class="header-right">
            <div class="download-btn">
                下载APP
            </div>
        </div>
    </header>
    <script src="./js/flexible.js"></script>
</body>

</html>

js相关代码：

(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';
    }
})();