mounted(){
    let yclientHeight=document.documentElement.clientHeight //原来的可视高度
    window.onresize = () => {
      let bclientHeight=document.documentElement.clientHeight //变化后的可视高度
      let scrollHeight=yclientHeight-bclientHeight//虚拟键盘的高度
         document.querySelector('.add-contact-box').style.top=-scrollHeight+'px'
      };
  },