function cssStyle2DomStyle(sName) {
  const reg = /-\w/g
  const matchArr = sName.match(reg)
  matchArr.forEach((item) => {
    sName = sName.replace(item, function (val, index) {
      const splitArr = val.split('')
      if (index === 0) {
        return splitArr[1]
      } else {
        return splitArr[1].toUpperCase()
      }
    })
  })
  return sName
}
console.log(cssStyle2DomStyle('font-size'))