• flexible.js


    ;(function(win, lib) {
    var doc = win.document;
    var docEl = doc.documentElement;
    var metaEl = doc.querySelector('meta[name="viewport"]');
    var flexibleEl = doc.querySelector('meta[name="flexible"]');
    var dpr = 0;
    var scale = 0;
    var tid;
    var flexible = lib.flexible || (lib.flexible = {});

    if (metaEl) {
    console.warn('将根据已有的meta标签来设置缩放比例');
    var match = metaEl.getAttribute('content').match(/initial-scale=([d.]+)/);
    if (match) {
    scale = parseFloat(match[1]);
    dpr = parseInt(1 / scale);
    }
    } else if (flexibleEl) {
    var content = flexibleEl.getAttribute('content');
    if (content) {
    var initialDpr = content.match(/initial-dpr=([d.]+)/);
    var maximumDpr = content.match(/maximum-dpr=([d.]+)/);
    if (initialDpr) {
    dpr = parseFloat(initialDpr[1]);
    scale = parseFloat((1 / dpr).toFixed(2));
    }
    if (maximumDpr) {
    dpr = parseFloat(maximumDpr[1]);
    scale = parseFloat((1 / dpr).toFixed(2));
    }
    }
    }
    if (!dpr && !scale) {
    var isAndroid = win.navigator.appVersion.match(/android/gi);
    var isIPhone = win.navigator.appVersion.match(/iphone/gi);
    var devicePixelRatio = win.devicePixelRatio;
    if (isIPhone) {
    // iOS下,对于2和3的屏,用2倍的方案,其余的用1倍方案
    if (devicePixelRatio >= 3 && (!dpr || dpr >= 3)) {
    dpr = 3;
    } else if (devicePixelRatio >= 2 && (!dpr || dpr >= 2)){
    dpr = 2;
    } else {
    dpr = 1;
    }
    } else {
    // 其他设备下,仍旧使用1倍的方案
    dpr = 1;
    }
    scale = 1 / dpr;
    }
    docEl.setAttribute('data-dpr', dpr);
    if (!metaEl) {
    metaEl = doc.createElement('meta');
    metaEl.setAttribute('name', 'viewport');
    metaEl.setAttribute('content', 'initial-scale=' + scale + ', maximum-scale=' + scale + ', minimum-scale=' + scale + ', user-scalable=no');
    if (docEl.firstElementChild) {
    docEl.firstElementChild.appendChild(metaEl);
    } else {
    var wrap = doc.createElement('div');
    wrap.appendChild(metaEl);
    doc.write(wrap.innerHTML);
    }
    }
    function refreshRem(){
    var width = docEl.getBoundingClientRect().width;
    if (width / dpr > 540) {
    width = 540 * dpr;
    }
    var rem = width / 10;
    docEl.style.fontSize = rem + 'px';
    flexible.rem = win.rem = rem;
    }
    win.addEventListener('resize', function() {
    clearTimeout(tid);
    tid = setTimeout(refreshRem, 300);
    }, false);
    win.addEventListener('pageshow', function(e) {
    if (e.persisted) {
    clearTimeout(tid);
    tid = setTimeout(refreshRem, 300);
    }
    }, false);
    if (doc.readyState === 'complete') {
    doc.body.style.fontSize = 12 * dpr + 'px';
    } else {
    doc.addEventListener('DOMContentLoaded', function(e) {
    doc.body.style.fontSize = 12 * dpr + 'px';
    }, false);
    }

    refreshRem();
    flexible.dpr = win.dpr = dpr;
    flexible.refreshRem = refreshRem;
    flexible.rem2px = function(d) {
    var val = parseFloat(d) * this.rem;
    if (typeof d === 'string' && d.match(/rem$/)) {
    val += 'px';
    }
    return val;
    }
    flexible.px2rem = function(d) {
    var val = parseFloat(d) / this.rem;
    if (typeof d === 'string' && d.match(/px$/)) {
    val += 'rem';
    }
    return val;
    }
    })(window, window['lib'] || (window['lib'] = {}));

    这段代码所做的主要事情就是把

    1rem的大小定义为屏幕宽度的十分之一

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  • 原文地址:https://www.cnblogs.com/mingweiyard/p/9025213.html
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