App.jsx

// App.js
// using .jsx extension because gist syntax
// highlighting chokes on `export default`
import ComponentA from './ComponentA'

export default {
  // use another component, in this scope only.
  // ComponentA maps to the tag <component-a>
  components: { ComponentA },
  template: `
    <div>
      <p>Now I'm using another component.</p>
      <component-a></component-a>
    </div>
  `
}

ComponentA.jsx

// ComponentA.js
export default {
  template: '<div>{{message}}</div>',
  data () {
    return {
      message: 'Hello!'
    }
  }
}