Vuejs 使用官网上面的例子

Question

1.使用vuejs 官网上面的例子，在控制台中发现了错误了，VM2369 vue.js:2658 [Vue warn]: Unknown custom element: <todo-item> - did you register the component correctly? For recursive components, make sure to provide the "name" option. (found in root instance)2.源码：<div id="app-7">   <ol>     <!-- Now we provide each todo-item with the todo object    -->     <!-- it's representing, so that its content can be dynamic -->     <todo-item v-for="item in groceryList" v-bind:todo="item"></todo-item>   </ol></div>Vue.component('todo-item', {  props: ['todo'],  template: '<li>{{ todo.text }}</li>'})var app7 = new Vue({  el: '#app-7',   data: {    groceryList: [       { text: 'Vegetables' },       { text: 'Cheese' },       { text: 'Whatever else humans are supposed to eat' }     ]   } })