移动端自动调整根元素字体大小

!function() {
    var a = "@charset \"utf-8\";html{color:#000;background:#fff;overflow-y:scroll;-webkit-text-size-adjust:100%;-ms-text-size-adjust:100%}html *{outline:0;-webkit-text-size-adjust:none;-webkit-tap-highlight-color:rgba(0,0,0,0)}html,body{font-family:sans-serif}body,div,dl,dt,dd,ul,ol,li,h1,h2,h3,h4,h5,h6,pre,code,form,fieldset,legend,input,textarea,p,blockquote,th,td,hr,button,article,aside,details,figcaption,figure,footer,header,hgroup,menu,nav,section{margin:0;padding:0}input,select,textarea{font-size:100%}table{border-collapse:collapse;border-spacing:0}fieldset,img{border:0}abbr,acronym{border:0;font-variant:normal}del{text-decoration:line-through}address,caption,cite,code,dfn,em,th,var{font-style:normal;font-weight:500}ol,ul{list-style:none}caption,th{text-align:left}h1,h2,h3,h4,h5,h6{font-size:100%;font-weight:500}q:before,q:after{content:''}sub,sup{font-size:75%;line-height:0;position:relative;vertical-align:baseline}sup{top:-.5em}sub{bottom:-.25em}a:hover{text-decoration:underline}ins,a{text-decoration:none}"
      , b = document.createElement("style");
    if (document.getElementsByTagName("head")[0].appendChild(b),
    b.styleSheet)
        b.styleSheet.disabled || (b.styleSheet.cssText = a);
    else
        try {
            b.innerHTML = a
        } catch (c) {
            b.innerText = a
        }
}();

!function(a, b) {
    function c() {
        var b = f.getBoundingClientRect().width;
        b / i > 640 && (b = 640 * i);
        var c = b / 10;
        f.style.fontSize = c + "px",
        k.rem = a.rem = c
    }
    var d, e = a.document, f = e.documentElement, g = e.querySelector('meta[name="viewport"]'), h = e.querySelector('meta[name="flexible"]'), i = 0, j = 0, k = b.flexible || (b.flexible = {});
    if (g) {
        console.warn("将根据已有的meta标签来设置缩放比例");
        var l = g.getAttribute("content").match(/initial\-scale=([\d\.]+)/);
        l && (j = parseFloat(l[1]),
        i = parseInt(1 / j))
    } else if (h) {
        var m = h.getAttribute("content");
        if (m) {
            var n = m.match(/initial\-dpr=([\d\.]+)/)
              , o = m.match(/maximum\-dpr=([\d\.]+)/);
            n && (i = parseFloat(n[1]),
            j = parseFloat((1 / i).toFixed(2))),
            o && (i = parseFloat(o[1]),
            j = parseFloat((1 / i).toFixed(2)))
        }
    }
    if (!i && !j) {
        var p = (a.navigator.appVersion.match(/android/gi),
        a.navigator.appVersion.match(/iphone/gi))
          , q = a.devicePixelRatio;
        i = p ? q >= 3 && (!i || i >= 3) ? 3 : q >= 2 && (!i || i >= 2) ? 2 : 1 : 1,
        j = 1 / i
    }
    if (f.setAttribute("data-dpr", i),
    !g)
        if (g = e.createElement("meta"),
        g.setAttribute("name", "viewport"),
        g.setAttribute("content", "initial-scale=" + j + ", maximum-scale=" + j + ", minimum-scale=" + j + ", user-scalable=no"),
        f.firstElementChild)
            f.firstElementChild.appendChild(g);
        else {
            var r = e.createElement("div");
            r.appendChild(g),
            e.write(r.innerHTML)
        }
    a.addEventListener("resize", function() {
        clearTimeout(d),
        d = setTimeout(c, 300)
    }, !1),
    a.addEventListener("pageshow", function(a) {
        a.persisted && (clearTimeout(d),
        d = setTimeout(c, 300))
    }, !1),
    "complete" === e.readyState ? e.body.style.fontSize = 12 * i + "px" : e.addEventListener("DOMContentLoaded", function() {
        e.body.style.fontSize = 12 * i + "px"
    }, !1),
    c(),
    k.dpr = a.dpr = i,
    k.refreshRem = c,
    k.rem2px = function(a) {
        var b = parseFloat(a) * this.rem;
        return "string" == typeof a && a.match(/rem$/) && (b += "px"),
        b
    }
    ,
    k.px2rem = function(a) {
        var b = parseFloat(a) / this.rem;
        return "string" == typeof a && a.match(/px$/) && (b += "rem"),
        b
    }
}(window, window.lib || (window.lib = {}));