rem自适应

        (function(b, a) {
            var c = document.documentElement;

            function d() {
                var j = c.clientWidth;
                j = j < a ? j : a;
                c.style.fontSize = j / b * 100 + "px";
                var g = document.querySelector("html");
                var i = parseInt(j / b * 100);
                var e = i;
                var h = 0;
                while (true) {
                    var f = parseInt(window.getComputedStyle(g).fontSize);
                    var k = f - e;
                    if (Math.abs(k) >= 1) {
                        if (k > 0) {
                            i--
                        } else {
                            i++
                        }
                        g.setAttribute("style", "font-size:" + i + "px!important")
                    } else {
                        break
                    }
                    if (h++ > 100) {
                        break
                    }
                }
                document.body.style.visibility = 'visible'
            }
            document.addEventListener("DOMContentLoaded", d);
            window.addEventListener("resize", d)
        })(750, 1500);
        // size 设计图宽度 \n max 允许设备最大宽度