rem 的js计算代码

!function(e){var t=e.document,n=t.documentElement,i="orientationchange"in e?"orientationchange":"resize",a=function e(){var t=n.getBoundingClientRect().width;return n.style.fontSize=5*Math.max(Math.min(t/750*20,11.2),8.55)+"px",e}();n.setAttribute("data-dpr",e.navigator.appVersion.match(/iphone/gi)?e.devicePixelRatio:1),/iP(hone|od|ad)/.test(e.navigator.userAgent)&&(t.documentElement.classList.add("ios"),parseInt(e.navigator.appVersion.match(/OS (\d+)_(\d+)_?(\d+)?/)[1],10)>=8&&t.documentElement.classList.add("hairline")),t.addEventListener&&(e.addEventListener(i,a,!1),t.addEventListener("DOMContentLoaded",a,!1))}(window);