checkbox-1

index.html

<div id="app">
  <input type="checkbox" id="chk" v-model="agree">
  <label for="chk">agree</label>
  <h1>{{agree}}</h1>
  <button @click="submit">submit</button>
</div>

script.js

new Vue({
  el:"#app",
  data:{
    agree: false,
  },
  methods:{
    submit(){
      if( this.agree !== true){
        alert('agreeeeeeee');
        return
      }
    // 表單送出後要做的事情...
    }
  }
})