JS限制手机端样式代码

<script>/** * YDUI 可伸缩布局方案 * rem计算方式：设计图尺寸px / 100 = 实际rem  例: 100px = 1rem */!function (window) {    /* 设计图文档宽度 */    var docWidth = 640;    var doc = window.document,        docEl = doc.documentElement,        resizeEvt = 'orientationchange' in window ? 'orientationchange' : 'resize';    var recalc = (function refreshRem () {        var clientWidth = docEl.getBoundingClientRect().width;        /* 8.55：小于320px不再缩小，11.2：大于420px不再放大 */        docEl.style.fontSize = Math.max(Math.min(20 * (clientWidth / docWidth), 11.2), 8.55) * 5 + 'px';        return refreshRem;    })();    /* 添加倍屏标识，安卓为1 */    docEl.setAttribute('data-dpr', window.navigator.appVersion.match(/iphone/gi) ? window.devicePixelRatio : 1);    if (/iP(hone|od|ad)/.test(window.navigator.userAgent)) {        /* 添加IOS标识 */        doc.documentElement.classList.add('ios');        /* IOS8以上给html添加hairline样式，以便特殊处理 */        if (parseInt(window.navigator.appVersion.match(/OS (\d+)_(\d+)_?(\d+)?/)[1], 10) >= 8)            doc.documentElement.classList.add('hairline');    }    if (!doc.addEventListener) return;    window.addEventListener(resizeEvt, recalc, false);    doc.addEventListener('DOMContentLoaded', recalc, false);}(window);</script>