CSS中使用Flexbox来达到居中效果的方法实现

.Center-Container.is-Flexbox {   
  display: -webkit-box;   
  display: -moz-box;   
  display: -ms-flexbox;   
  display: -webkit-flex;   
  display: flex;   
  -webkit-box-align: center;   
     -moz-box-align: center;   
     -ms-flex-align: center;   
  -webkit-align-items: center;   
          align-items: center;   
  -webkit-box-pack: center;   
     -moz-box-pack: center;   
     -ms-flex-pack: center;   
  -webkit-justify-content: center;   
          justify-content: center;   
}