App.vue
main.js
 
<template>
  <h1>Select Multiple in Vue</h1>
  <p>Depending on your operating system, use the 'ctrl' or the 'command' key to select multiple options.</p>
  <form @submit.prevent="registerAnswer">
    <label for="cars">Choose one or more cars:</label><br>
    <select  v-model="carsSelected" id="cars" multiple>
      <option>Volvo</option>
      <option>Saab</option>
      <option>Opel</option>
      <option>Audi</option>
      <option>Kia</option>
    </select>
    <button type="submit">Submit</button>
  </form>
  <div>
    <h3>Submitted answer:</h3>
    <p id="pAnswer">{{ inpValSubmitted }}</p>
  </div>
</template>

<script>
export default {
  data() {
    return {
      carsSelected: [],
      inpValSubmitted: 'Not submitted yet'
    }
  },
  methods: {
    registerAnswer() {
      if(this.carsSelected) {
        this.inpValSubmitted = this.carsSelected;
      }
    }
  }
}
</script>

<style scoped>
  div {
    border: dashed black 1px;
    border-radius: 10px;
    padding: 0 20px 20px 20px;
    margin-top: 20px;
    display: inline-block;
  }
  button, select {
    margin: 10px;
    display: block;
  }
  label {
    width: 80px;
    padding: 5px;
  }
  label:hover {
    cursor: pointer;
    background-color: rgb(211, 244, 211);
    border-radius: 5px;
  }
  #pAnswer {
    background-color: lightgreen;
    padding: 5px;
  }
</style>                  
import { createApp } from 'vue'

import App from './App.vue'

const app = createApp(App)
app.mount('#app')
                  
http://localhost:5173/