demo

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>lesson 20</title>
  <script src="https://unpkg.com/vue@next"></script>
</head>
<body>
  <div id="root"></div>
</body>
<script>
  // 作用域插槽
  const app = Vue.createApp({
    template: `
      <list v-slot="{item}">
        <div>{{item}}</div>
      </list>
    `
  });

  app.component('list', {
    data() {return {list: [1, 2, 3]}},
    template: `
      <div>
        <slot v-for="item in list" :item="item" />
      </div>
    `
  });

  const vm = app.mount('#root');
</script>
</html>
<slot v-for="item in list" :item="item" /> 这里传递的是数据 由父组件传递  
v-slot="{item}" 表示将父组件传递过来的数据结构出来
越努力越幸运