//淘宝
(function flexible(window, document) {
    var docEl = document.documentElement;
    var tid;
    var dpr = window.devicePixelRatio || 1; //获取到当前设备的dpr
    docEl.setAttribute("data-dpr", dpr);

    function setRemUnit() {
        var width = docEl.getBoundingClientRect().width;
        if (width > 750) { // 设计稿的宽度是750px
            docEl.style.fontSize = 100 + 'px';
        }
        else {
            var rem = width / 7.5;
            docEl.style.fontSize = rem + 'px';
        }
    }

    setRemUnit();

    window.addEventListener('resize', function () {
        clearTimeout(tid);
        tid = setTimeout(setRemUnit, 200);
    }, false);
    window.addEventListener('pageshow', function (e) {
        if (e.persisted) {
            clearTimeout(tid);
            tid = setTimeout(setRemUnit, 200);
        }
    }, false);
}(window, document));

window.addEventListener("load", function () {
    setTimeout(function () {
        window.scrollTo(0, 0);
    }, 0);
}, false);

<!--耗时0.0087280273秒-->