var iwidth = 1920; //pc端以1920的设计稿为基准
var iminwidth = 1020; //可视宽度小于1020，显示移动端效果图，以750的设计稿为基准
var e = window.document,
    t = e.documentelement,
    i = iwidth,
    d = i / 100,
//  d = i / 100,
    o = "orientationchange" in window ? "orientationchange" : "resize",
    a = function() {
        var n = t.clientwidth || 320;
        if (n >= iminwidth) {
            //宽度为1920时，html的font-size=100px
            t.style.fontsize = n / d + "px";
        } else {
            //宽度为750时，html的font-size=100px, 使用vw单位
            t.style.fontsize = (100 / 750) * 100 + "vw";
        }
    };
e.addeventlistener &&
    (window.addeventlistener(o, a, !1),
        e.addeventlistener("domcontentloaded", a, !1));