用户体验与响应式字体二三事｜rem单位与flexible.js、rpx单位与css媒体查询

// 首先是一个立即执行函数，执行时传入的参数是window和document
(function flexible (window, document) {
  var docEl = document.documentElement  // 返回文档的root元素
  var dpr = window.devicePixelRatio || 1 // 获取设备的dpr，即当前设置下物理像素与虚拟像素的比值

  // adjust body font size 设置默认字体大小，默认的字体大小继承自body
  function setBodyFontSize () {
    if (document.body) {
      document.body.style.fontSize = (12 * dpr) + 'px'
    }
    else {
      document.addEventListener('DOMContentLoaded', setBodyFontSize)
    }
  }
  setBodyFontSize();

  // set 1rem = viewWidth / 10
  function setRemUnit () {
    var rem = docEl.clientWidth / 10
    docEl.style.fontSize = rem + 'px'
  }

  setRemUnit()

  // reset rem unit on page resize
  window.addEventListener('resize', setRemUnit)
  window.addEventListener('pageshow', function (e) {
    if (e.persisted) {
      setRemUnit()
    }
  })

  // detect 0.5px supports  检测是否支持0.5像素，解决1px在高清屏多像素问题，需要css的配合。
  if (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))

px2rem: {
    open: true, // 如果要开启，需要设置为 true
    loader: 'px2rem-loader', // 开发者在当前目录需要自行安装 px2rem-loader: npm i px2rem-loader
    options: {
        remUnit: 75
    }
},

@media screen and (width:360px){html{font-size:48px}}
@media screen and (width:375px){html{font-size:50px}}
@media screen and (width:414px){html{font-size:55.2px}}
@media screen and (width:480px){html{font-size:64px}}
@media screen and (width:540px){html{font-size:72px}}
@media screen and (min-width:750px){html{font-size:100px}}