三部分实现todoList

//todoHeader组件
<template>
    <div>
    	//数据双向绑定,trim去除空格,keyup实现按回车键添加一条todo列表
        <input v-model.trim="text" @keyup.enter="addTodo">
        <button @click="addTodo">addtodo</button>
    </div>
</template>

<script>
export default {
    data(){
        return{
            text:""
        }
    },
    methods:{
        addTodo(){
        //输入框有内容才能发送
            if(this.text){
            	//自定义一条todo,id为时间戳
                let todo={id:+new Date(),text:this.text,completed:false}
                //这里使用子组件反向传值修改父组件的值,把自定义的todo传过去
                this.$emit("add-todo",todo)
            }
            //输入完内容再清空输入框
            this.text=""
        }
    }
}
</script>

//todoList组件
<template>
    <div>
    //动态绑定class,todo处于完成状态时添加completed类名
        <div v-for="todo in todos" :key="todo.id" :class="{completed:todo.completed}">
        //动态绑定复选框勾选属性,根据todo已完成未完成状态
            <input type="checkbox" :checked="todo.completed" 
            //改变输入内容时自动触发,也是反向传值修改父组件,切换完成状态
            @change="$emit('toggle-completed',todo.id)"/>
            {
   {todo.text}}
            //删除一条todo,同样反向传值
            <button @click="$emit('remove-todo',todo.id)">删除</button>
        </div>
    </div>
</template>

<script>
export default {
	//接受父组件传递过来的todos列表
    props:["todos"],
}
</script>

<style scoped>
  .completed{
      color:#ccc;
      text-decoration: line-through;
  }
</style>

//todoFilter组件
<template>
    <div class="filter-box">
    //切换所有todo,未完成todo,已完成todo状态,根据filter的值切换当前状态,点击时候触发的切换也是通过反向传值
        <span class="filter-btn" :class="{active:filter===0}" @click="$emit('set-filter',0)">All</span>
        <span class="filter-btn" :class="{active:filter===1}" @click="$emit('set-filter',1)">Active</span>
        <span class="filter-btn" :class="{active:filter===2}" @click="$emit('set-filter',2)">Completed</span>
    </div>
</template>

<script>
export default {
//接受父组件传递过来的filter
    props:["filter"]
}
</script>

<style scoped>
    .filter-box{
        margin-top:10px;
    }
    .filter-btn{
        display:inline-block;
        border:1px solid #ccc;
        padding:3px;
        margin-left:10px;
        color:#ccc;
    }
    .active{
        border:1px solid blue;
        color:blue;
    }
</style>

//App.vue应用主组件
<template>
  <div id="app">
  	//使用组件,并定义自定义事件
    <TodoHeader @add-todo="addTodo"></TodoHeader>
    //注意,这里之前是:todos="todos",现在换成了计算属性的toggleTodo
    <TodoList :todos="toggleTodo" @remove-todo="removeTodo" @toggle-completed="toggleCompleted"></TodoList>
    <TodoFilter :filter="filter" @set-filter="setFilter"></TodoFilter>
  </div>
</template>
<script>
//引入三个组件
import TodoList from "./components/TodoList"
import TodoHeader from "./components/TodoHeader"
import TodoFilter from "./components/TodoFilter"
export default {
  data(){
    return{
    //存储todos原数据
      todos:[
        {id:0,text:"好好学习",completed:true},
        {id:1,text:"天天向上",completed:true},
        {id:2,text:"热爱生活",completed:false},
        {id:3,text:"酷爱运动",completed:true},
      ],
      //定义filter初始值
      filter:0
    }
  },
  computed:{
  //使用计算属性来监听todo状态变化,达到切换所有todo的所有,未完成和已完成状态
    toggleTodo(){
      return this.todos.filter(todo => {
      //当filter为1的时候就是展示未完成的todo
        if(this.filter === 1){
          return !todo.completed
        }
        //filter为2的时候展示已完成的todo
        if(this.filter === 2){
          return todo.completed
        }
        //默认展示所有的todo
        return true
      })
    }
  },
  methods:{
  //添加一条todo方法
    addTodo(todo){
      this.todos.push(todo)
    },
    //切换todo的已完成未完成状态
    toggleCompleted(id){
    //map修改数组的一项或多项
      this.todos=this.todos.map(todo => {
      //如果todo.id等于传进来的id就修改
        if(todo.id === id){
        //保留原todo,修改todo状态
          return {...todo,completed:!todo.completed}
        }
        return todo
      })
    },
    //删除一条todo
    removeTodo(id){
    //filter过滤,实现删除功能,把当前点击的id相等的todo删掉
      this.todos=this.todos.filter(todo => todo.id != id)
    },
    //设置filter的值为当前传递的值
    setFilter(filter){
        this.filter = filter
    }
  },
  components:{
  //注册组件
    TodoList,
    TodoHeader,
    TodoFilter
  },

}
</script>
<style>

</style>

以下为效果图