rem 手机屏幕适配

手机端屏幕适配解决方案(含屏幕旋转):

function adapt(designWidth, rem2px){
  var d = window.document.createElement('div');
  d.style.width = '1rem';
  d.style.display = "none";
  var head = window.document.getElementsByTagName('head')[0];
  head.appendChild(d);
  var defaultFontSize = parseFloat(window.getComputedStyle(d, null).getPropertyValue('width'));
  d.remove();
  document.documentElement.style.fontSize = window.innerWidth / designWidth * rem2px / defaultFontSize * 100 + '%';
  var st = document.createElement('style');
  var portrait = "@media screen and (min-width: "+window.innerWidth+"px) {html{font-size:"+((window.innerWidth/(designWidth/rem2px)/defaultFontSize)*100) +"%;}}";
  var landscape = "@media screen and (min-width: "+window.innerHeight+"px) {html{font-size:"+((window.innerHeight/(designWidth/rem2px)/defaultFontSize)*100) +"%;}}"
  st.innerHTML = portrait + landscape;
  head.appendChild(st);
  return defaultFontSize
};
var defaultFontSize = adapt(640, 100);

danhuan 阅读笔记 2018.04.02
文章：https://mp.weixin.qq.com/s/JIRN56acxvJgmzk1Fjj6LA

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