IE 兼容

方法默认传参

• 不推荐 | function showName(name = ‘’){
  console.log(name)} | | :—- |

• 推荐 | function showName(name){
  name = name || ‘’ console.log(name)} | | :—- |

选择器

• 推荐

  $('.calssName').attr()

• 不推荐

  $('.calssName')[0].attr()