<div id="box">              
 位置
 <br>x:{{val.x}} <br>y:{{val.y}}
 <div v-drag="greet" id="drag" :>
 //注意這里要通過指令綁定函數將當前元素的位置數據傳出來
 </div>
</div>

Vue.directive('drag',//自定義指令          

  {bind:function (el, binding) {
    let oDiv = el; //當前元素
    let self = this; //上下文
    oDiv.onmousedown = function (e) {
     //鼠標按下，計算當前元素距離可視區的距離
     let disX = e.clientX - oDiv.offsetLeft;
     let disY = e.clientY - oDiv.offsetTop;

     document.onmousemove = function (e) {
      //通過事件委托，計算移動的距離 
      let l = e.clientX - disX;
      let t = e.clientY - disY;
      //移動當前元素 
      oDiv.style.left = l + 'px';
      oDiv.style.top = t + 'px';
       //將此時的位置傳出去
      binding.value({x:e.pageX,y:e.pageY})
     };
     document.onmouseup = function (e) {
     
      document.onmousemove = null;
      document.onmouseup = null;
      };
    };
   }
  }
 );
 window.onload = function () {
  let vm = new Vue({
   el: '#box',
   data: {
    val: '123',
    style: {
     width: '100px',
     height: '100px',
     background: 'aqua',
     position: 'absolute',
     right: '30px',
     top: 0
    }
   },
   methods:{
   //接受傳來的位置數據，并將數據綁定給data下的val
    greet(val){
     vm.val = val;
    }
   } ,
  });
 }