动态设置rem的大小

基于iphone6屏幕

!function (n) {
        var e = n.document, 
        t = e.documentElement, 
        i = 750, 
        d = i / 100, 
        o = "orientationchange" in n ? "orientationchange" : "resize", 
        a = function () {
          var n = t.clientWidth || 375;
          n > 750 && (n = 750), t.style.fontSize = n / d + "px"
        };
        e.addEventListener && (n.addEventListener(o, a, !1), 
        e.addEventListener("DOMContentLoaded", a, !1))
}(window);