src/index.js
function getIEVersion () {
  var agent = navigator.userAgent
  var reg = /MSIE\s?(\d+)(?:\.(\d+))?/i
  var matches = agent.match(reg)
  if (matches != null) {
    return { major: matches[1], minor: matches[2] }
  }
  return { major: '-1', minor: '-1' }
}
function getIEVersion () {
  var agent = navigator.userAgent
  var reg = /MSIE\s?(\d+)(?:\.(\d+))?/i
  var matches = agent.match(reg)
  if (matches != null) {
    return { major: matches[1], minor: matches[2] }
  }
  return { major: '-1', minor: '-1' }
}
ie10以及以下，对某些样式支持有问题，需要降级