http://yyvcc.com/utils/index.js

1(function flexible(window, document) {
2    var docEl = document.documentElement;
3    var dpr = window.devicePixelRatio || 1;
4
5    // adjust body font size
6    function setBodyFontSize() {
7        if (document.body) {
8            document.body.style.fontSize = 12 * dpr + "px";
9        } else {
10            document.addEventListener("DOMContentLoaded", setBodyFontSize);
11        }
12    }
13    setBodyFontSize();
14
15    // set 1rem = viewWidth / 10
16    function setRemUnit() {
17        var rem = docEl.clientWidth / 24; // 这里默认是10等份，手动改为24，此时1rem=1920/24px即80px。（设计稿是1920px的）
18        docEl.style.fontSize = rem + "px";
19    }
20    setRemUnit();
21
22    // reset rem unit on page resize
23    window.addEventListener("resize", setRemUnit);
24    window.addEventListener("pageshow", function(e) {
25        if (e.persisted) {
26            setRemUnit();
27        }
28    });
29
30    // detect 0.5px supports
31    if (dpr >= 2) {
32        var fakeBody = document.createElement("body");
33        var testElement = document.createElement("div");
34        testElement.style.border = ".5px solid transparent";
35        fakeBody.appendChild(testElement);
36        docEl.appendChild(fakeBody);
37        if (testElement.offsetHeight === 1) {
38            docEl.classList.add("hairlines");
39        }
40        docEl.removeChild(fakeBody);
41    }
42})(window, document);