关于移动端rem适配

var num = 1 / window.devicePixelRatio;
var fontSize = document.documentElement.clientWidth / 10;
document.getElementsByTagName('html')[0].style.fontSize = fontSize + 'px';

适配移动端rem单位，实际使用的时候用量取到的像素值/75即为计算后的rem值，标准为iPhone6的750的尺寸。750px的设计稿的标准宽度为10rem；

补充另一种，本质不变

!function (a, d) {
    function c() {
        var t = document.documentElement.clientWidth,
            i = document.documentElement.clientHeight;
        d.documentElement.style.fontSize = ((t / i) >= 0.75) ? t * 0.1 + "px" : t / 750 * 75 + "px"
    };
    var b = null;
    a.addEventListener("onorientationchange" in a ? "orientationchange" : "resize", function () {
        clearTimeout(b);
        b = setTimeout(c, 300)
    }, !1);
    a.addEventListener("pageshow", function (a) {
        a.persisted && (clearTimeout(b), b = setTimeout(c, 300))
    }, !1);
    d.addEventListener("DOMContentLoaded", c, false)
}(window, document);