Vue.directive('drag', {
 inserted: function (el) {
  el.onmousedown=function(ev){
   var disX=ev.clientX-el.offsetLeft;
   var disY=ev.clientY-el.offsetTop;
   document.onmousemove=function(ev){
    var l=ev.clientX-disX;
    var t=ev.clientY-disY;
    el.style.left=l+'px';
    el.style.top=t+'px';
   };
   document.onmouseup=function(){
    document.onmousemove=null;
    document.onmouseup=null;

   };
  };
 }

})

directives: {
 drag: {
  // 使用bind會有可能沒有渲染完成
  inserted: function(el, binding, vnode) {
  const _el = el; //獲取當(dāng)前元素
  const ref = vnode.context.$refs[binding.value]; // 判斷基于移動的是哪一個(gè)盒子
  const masterNode = ref ? ref : document; // 用于綁定事件
  const masterBody = ref ? ref : document.body; // 用于獲取高和寬
  const mgl = _el.offsetLeft;
  const mgt = _el.offsetTop;
  const maxWidth = masterBody.clientWidth;
  const maxHeight = masterBody.clientHeight;
  const elWidth = _el.clientWidth;
  const elHeight = _el.clientHeight;
  let positionX = 0,
   positionY = 0;
  _el.onmousedown = e => {
   //算出鼠標(biāo)相對元素的位置，加上的值是margin的值
   let disX = e.clientX - _el.offsetLeft + mgl; 
   let disY = e.clientY - _el.offsetTop + mgt;
   masterNode.onmousemove = e => {
   //用鼠標(biāo)的位置減去鼠標(biāo)相對元素的位置，得到元素的位置
   let left = e.clientX - disX;
   let top = e.clientY - disY;
   // 綁定的值不能滑出基于盒子的范圍
   left < 0 && (left = 0);
   left > (maxWidth - elWidth - mgl) && (left = maxWidth - elWidth - mgl);
   top < 0 && (top = 0);
   top > (maxHeight - elHeight - mgt) && (top = maxHeight - elHeight - mgt);
   //綁定元素位置到positionX和positionY上面
   positionX = top;
   positionY = left;
   
   //移動當(dāng)前元素
   _el.style.left = left + "px";
   _el.style.top = top + "px";
   };
   // 這里是鼠標(biāo)超出基于盒子范圍之后再松開，會監(jiān)聽不到
   document.onmouseup = e => {
   masterNode.onmousemove = null;
   document.onmouseup = null;
   };
  };
  }
 }
 }