ReviewForm.js

app.component('review-form', {
  template:
    /*html*/
    `
    <form class="review-form" @submit.prevent="onSubmit">
      <h3>Leave a review</h3>

      <label for="name">Name:</label>
      <input id="name" v-model="name">
    
      <label for="review">Review:</label>      
      <textarea id="review" v-model="text"></textarea>

      <label for="rating">Rating:</label>
      <select id="rating" v-model.number="rating">
        <option>5</option>
        <option>4</option>
        <option>3</option>
        <option>2</option>
        <option>1</option>
      </select>
  
      <input class="button" type="submit" value="Submit">  
    
    </form>
  `,
  data() {
    return {
      name: '',
      text: '',
      rating: null
    }
  },
  methods: {
    onSubmit() {
      if (this.name === '' || this.text === '' || this.rating === null) {
        alert('Review is incomplete. Please fill out every field.')
        return
      }

      const review = {
        name: this.name,
        text: this.text,
        rating: this.rating
      }
      this.$emit('review-submitted', review)
      this.name = ''
      this.text = ''
      this.rating = null
    }
  }
})