vue.js 的一些问题

1.必须加key要不然有警告。

2.先注册组件，再新建Vue.

例如：

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' }
    ]
  }

Unknown custom element:  - did you register the component correctly? For recursive components, make sure to provide the "name" option.
(found in root instance)