var app = new Vue({
            el: '#app',
            components: {
                TodoList: TodoList,
            },
            data: {
                message: 'hello world',
                listcontent: [],
            },
            methods: {
                submit: () => {
                    app.listcontent.push(app.message);
                    app.message = '';
                },
                handleItemDelete: (index) => {
                    app.listcontent.splice(index, 1);
                }
            },
            computed: {
                    computedMessage:function(){
                        return this.$data.listcontent===this.listcontent;
                    }
            }
        });