the code is as follows:
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title></title>
    <script src="https://cdn.jsdelivr.net/npm/vue@2.5.16/dist/vue.js"></script>
</head>
<style>
    ul li {
        list-style: none;
    }
    .done {
        text-decoration: line-through;
        color: indianred;
    }
</style>
<body>
<div id="app">
    <div>
        3 of {{todo.length}} remaning[arctive]
        <ul>
            <li v-for="(item,index) of todo" :key="item.index">
                <input type="checkbox" v-model="item.done">
                <span :class="{done:item.done}">{{item.id}}---{{item.content}}</span>
                <button @click="deleteClick(index)">X</button>
            </li>
        </ul>
    </div>
    <input type="text" v-model="todoText" @keydown.enter="addToClick">
    <button @click="addToClick"></button>
</div>
<script>
    const app = new Vue({
        el: "-sharpapp",
        data: {
            todoText: "",
            todo: [
                {id: 1, content: "FOO", done: true},
            ],
        },
        methods: {
            addToClick: function () {
                if (this.todoText === "") {//
                    return
                }
                this.todo.push({
                    id: this.todo[this.todo.length - 1].id + 1,
                    content: this.todoText.trim(),
                    done: false
                });
                this.todoText = "";
            },
            deleteClick: function (index) {
                console.log(index);
                this.todo.splice(index, 1);
            }
        }
    })
</script>
</body>
</html>
there is a requirement:
 
 
 when I click on the 8th, delete it, and the following 9Magol 10. 11 becomes 8jin9. 10. and so on. Do you need to re-render the deleteClick during the click event? 
 which experienced friend should I ask? Thank you 
