移动端rem布局方法

750px的psd设计稿，

1、自适应@media设置，取值x/20 rem；

@media only screen and (min-width: 241px) and (max-width: 320px) {
  html {
    font-size: 8.53px !important
  }
}

@media only screen and (min-width: 321px) and (max-width: 360px) {
  html {
    font-size: 9.6px !important
  }
}

@media only screen and (min-width: 361px) and (max-width: 375px) {
  html {
    font-size: 10px !important
  }
}

@media only screen and (min-width: 376px) and (max-width: 384px) {
  html {
    font-size: 10.24px !important
  }
}

@media only screen and (min-width: 385px) and (max-width: 414px) {
  html {
    font-size: 11.04px !important
  }
}

@media only screen and (min-width: 415px) and (max-width: 480px) {
  html {
    font-size: 12.8px !important
  }
}

@media only screen and (min-width: 481px) and (max-width: 600px) {
  html {
    font-size: 13px !important
  }
}

@media screen and (min-width: 601px) {
  html {
    font-size: 14px !important
  }
}

 2、淘宝，取值x/75rem

<script>
        !function (a, b) {
            function c() {
                var b = f.getBoundingClientRect().width;
                b / i > 540 && (b = 540 * 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.userAgent, q = (!!p.match(/android/gi), !!p.match(/iphone/gi)), r = q && !!p.match(/OS 9_3/), s = a.devicePixelRatio;
                i = q && !r ? s >= 3 && (!i || i >= 3) ? 3 : s >= 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 t = e.createElement("div");
                t.appendChild(g), e.write(t.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 = {}));
    </script>