rem.js

(function flexible(window, document) {var docEl = document.documentElement;var dpr = window.devicePixelRatio || 1;// adjust body font size// 设置 em 默认字体所对应的大小function setBodyFontSize() {if (document.body) {document.body.style.fontSize = 12 * dpr + "px";} else {document.addEventListener("DOMContentLoaded", setBodyFontSize);}}setBodyFontSize();// 将视窗分为多少份// set 1rem = viewWidth / 10function setRemUnit() {var rem = docEl.clientWidth / 10;docEl.style.fontSize = rem + "px";}setRemUnit();// 当页面发生改变时，重新设置 rem 所对应的刻度值// reset rem unit on page resizewindow.addEventListener("resize", setRemUnit);window.addEventListener("pageshow", function(e) {if (e.persisted) {setRemUnit();}});// detect 0.5px supportsif (dpr >= 2) {var fakeBody = document.createElement("body");var testElement = document.createElement("div");testElement.style.border = ".5px solid transparent";fakeBody.appendChild(testElement);docEl.appendChild(fakeBody);if (testElement.offsetHeight === 1) {docEl.classList.add("hairlines");}docEl.removeChild(fakeBody);}
})(window, document);