app.js

Vue.createApp({
  data() {
    return {
      valueInput: '',
      needDoList: [],
      completeList: []
    };
  },
  methods: {
    handleInput (event) {
      this.valueInput = event.target.value;
    },
    addTask () {
      if(this.valueInput === '') { return };
      this.needDoList.push({
        title: this.valueInput,
        id: Math.random()
      });
      this.valueInput = '';
    },
    doCheck (index, type) {

      if(type === 'need') {
        const completeMask = this.needDoList.splice(index, 1);
        this.completeList.push(...completeMask);
      }
      else {
        const noCompleteMask = this.completeList.splice(index, 1);
        this.needDoList.push(...noCompleteMask);
      }
    },
    removeMask (index, type) {
      const toDoList = type === 'need' ? this.needDoList : this.completeList;
      toDoList.splice(index, 1);
    }
  }
}
).mount('#app');