viewport实现html页面动态缩放/meta viewport/viewport

页面默认缩放比例为1，最小宽度为375px，在小于375px出现水平滚动条的时候重新计算显示比例缩小界面，
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="utf-8">
    <title>viewport</title>

    <meta id="viewport" name="viewport" content="width=device-width,initial-scale=1,maximum-scale=1,minimum-scale=1,user-scalable=no">
    <script type="text/javascript">
        var winW = window.innerWidth || document.documentElement.clientWidth || document.body.clientWidth, viewport = document.getElementById("viewport"), scale = 1;
        if (winW <= 320) {
            scale = winW / 375.00;
        }
        else if (winW < 395) {
            scale = (winW - 20) / 375.00;
        }
        if (winW < 395) {
            viewport.content = 'width=device-width,initial-scale=' + scale + ',maximum-scale=' + scale + ',minimum-scale=' + scale + ',user-scalable=no';
        }
    </script>

    <style>
        html, body {
            position: relative;
            height: 100%;
        }

        body {
            background: #eee;
            font-family: Helvetica Neue, Helvetica, Arial, sans-serif;
            font-size: 14px;
            color: #000;
            margin: 0;
            padding: 0;
        }

        .container {
            width: 768px;
            margin: 0 auto;
            height: 300px;
            box-shadow: 0 0 1px #bebebe;
        }

        @media (max- 768px) {
            .container {
                width: 576px;
            }
        }

        @media (max- 576px) {
            .container {
                width: 375px;
            }
        }

        p {
            word-wrap: break-word;
        }
    </style>
</head>
<body>

<div class="container">
    <h1>viewport</h1>
    <p>AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA</p>
</div>

</body>
</html>