App.vue
main.js
 
<template>
  <p>Using the '.prop' modifier to toggle the 'indeterminate' appearance of the checkbox:</p>
  <button v-on:click="indetVal = !indetVal">Toggle</button>
  <p>
    <input type="checkbox" v-bind:indeterminate.prop="indetVal"> Checkbox
  </p>
</template>

<script>
export default {
  data() {
    return {
      indetVal: false
    };
  }
};
</script>

<style>
input {
  margin: 20px;
  scale: 2;
}
</style>                  
import { createApp } from 'vue'

import App from './App.vue'

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