SOURCE

var vm3 = new Vue({
  el: '#app3',
  data: {
  	lis: {
      'id':[],
      'sku_id':[]
    },
    selected: [],
    ok: true
  },
  methods: {
    add: function(){
        if(this.ok){
          for(var i=0;i<this.lis.sku_id.length;i++){
             this.selected.push(this.lis.sku_id[i]);
          }
          this.ok = false;
        } else {
          this.selected = [];
          this.ok = true;
        }
    }
  }
})

<script src="https://cdn.bootcss.com/vue/2.3.4/vue.js"></script>
  <br><br>
  <div id="app3">
    <label>
      <input type="checkbox" value="2" v-model="lis.id" @click="add()">check
      <input type="hidden" value="8" v-model="lis.sku_id">
    </label>
    
    <br>
    <span>{{ lis.id }}</span>
    <span>{{ lis.sku_id }}</span>
    <span>{{ selected }}</span>
</div>