.shop{
  position: fixed;
  top: 300px;
  left: 40px;
 }
 .ball{
  position: fixed;
  left: 32px;
  bottom: 22px;
  z-index: 200;
  transition: all 0.4s cubic-bezier(0.49, -0.29, 0.75, 0.41); /*贝塞尔曲线*/
 }
 .inner{
  width: 16px;
  height: 16px;
  border-radius: 50%;
  background-color: rgb(0,160,220);
  transition: all 0.4s linear;
 }
 .cart{
  position: fixed;
  bottom: 22px;
  left: 32px;
  width: 30px;
  height: 30px;
  background-color: rgb(0,160,220);
  color: rgb(255,255,255);
 }

<div id="app">
  <ul class="shop">
   <li v-for="item in items">
    <span>{{item.text}}</span>
    <span>{{item.price}}</span>
    <button @click="additem">添加</button>
   </li>
  </ul>
 <div class="cart" style="">{{count}}</div>
  <div class="ball-container"><!--小球-->
   <div v-for="ball in balls">
    <transition name="drop" @before-enter="beforeDrop" @enter="dropping" @after-enter="afterDrop">
     <div class="ball" v-show="ball.show">
      <div class="inner inner-hook"></div>
     </div>
    </transition>
   </div>
  </div>
 </div>

<script>
  new Vue({
   el:"#app",
   data:{
    count: 0,
    items:[
     {
      text: "苹果",
      price: 15
     },
     {
      text: "香蕉",
      price: 15
     }
    ],
    balls: [ //小球 设为3个
     {
      show: false
     },
     {
      show: false
     },
     {
      show: false
     },
    ],
    dropBalls:[],
   },
   methods:{
    additem(event){
    this.drop(event.target);
    this.count ++;
    },
    drop(el){ //抛物
     for(let i=0;i<this.balls.length;i++){
      let ball= this.balls[i];
      if(!ball.show){
       ball.show = true;
       ball.el=el;
       this.dropBalls.push(ball);
       return;
      }
     }
    },
    beforeDrop(el) {/* 购物车小球动画实现 */
     let count = this.balls.length;
     while (count--) {
      let ball = this.balls[count];
      if (ball.show) {
       let rect = ball.el.getBoundingClientRect(); //元素相对于视口的位置
       let x = rect.left - 32;
       let y = -(window.innerHeight - rect.top - 22); //获取y
       el.style.display = '';
       el.style.webkitTransform = 'translateY('+y+'px)'; //translateY
       el.style.transform = 'translateY('+y+'px)';
       let inner = el.getElementsByClassName('inner-hook')[0];
       inner.style.webkitTransform = 'translateX('+x+'px)';
       inner.style.transform = 'translateX('+x+'px)';
      }
     }
   },
    dropping(el, done) { /*重置小球数量 样式重置*/
     let rf = el.offsetHeight;
     el.style.webkitTransform = 'translate3d(0,0,0)';
     el.style.transform = 'translate3d(0,0,0)';
     let inner = el.getElementsByClassName('inner-hook')[0];
     inner.style.webkitTransform = 'translate3d(0,0,0)';
     inner.style.transform = 'translate3d(0,0,0)';
     el.addEventListener('transitionend', done);
   },
    afterDrop(el) { /*初始化小球*/
     let ball = this.dropBalls.shift();
     if (ball) {
     ball.show=false;
     el.style.display = 'none';
    }
   }
  }
 })
 </script>