How to use react to implement todolist: 1. Create a new project folder Code; 2. Create a react project through the "create-react-app todo-list" command; 3. Create a new ToDoList under the components folder. jsx file; 4. Use an array to save data, and each element in the array is an object; 5. Write the page layout; 6. Add keyboard events, monitor input changes, and implement to-do items and completed items.
The operating environment of this tutorial: Windows 10 system, react18.0.0 version, Dell G3 computer.
How to implement todolist using react?
React Getting Started Practical Example - ToDoList Implementation
Summary:
I have been studying React for a short period of time recently and have a little understanding of the basics of some React development components. Following the teaching video, I implemented the function of a ToDoList component. Today I will record the process of making this component to deepen my learning impression. As a reference for the same front-end beginners.
Video 1.1
Before preparation: This article assumes development The environment has been configured, including:
1. Create a new project folder Code, use VSCode, and add the Code file to the workspace;
Figure 2.1
2. Right-click the Code folder and select Open in Terminal in the tab;
Figure 2.2
3. Enter the following command in the terminal to create a new React project: create-react-app todo-list
Figure 2.3
4. Generate the Rreact project as follows:
Figure 2.4
React development is mainly for src The files in are manipulated. node_modules mainly prevents various dependent packages, public places some public files, and package.json is some configuration files, which will not be described in detail here.
As shown in Figure 2.5:
Figure 2.5
Create a new ToDoList.jsx file in the components folder and write it as follows Code, set up the basic framework of a component; the code is as follows:
//导入React相关依赖
import React from 'react';
//创建一个组件
class ToDoList extends React.Component{
//构造函数
constructor(props){
super(props);
//this是父组件（类）的一个实例，实例就类似于java里的一个类，创建了这个类型的一个对象，这个对象就是实例
this.state = {
//this.state里可以写一些初始化的数据
}
}
//render渲染虚拟DOM
render(){
return(
<div>
ToDoList
</div>
);
}
}
//输出组件,使得该组件可以被其他组件调用
export default ToDoList;使用一个数组来保存数据，数组中每个元素为一个对象，该对象包括两个字段:title和checked,tile为字符串类型，checked为布尔类型，用来区分待办（false）和已办（true）;
list:[
{
title:'吃饭',
checked:true
},
{
title:'跑步',
checked:false
},
{
title:'上班',
checked:false
},
{
title:'睡觉',
checked:true
},
]该数组在this.state中初始化：
constructor(props){
super(props);
//this是父组件（类）的一个实例，实例就类似于java里的一个类，创建了这个类型的一个对象，这个对象就是实例
this.state = {
//this.state里可以写一些初始化的数据
list:[
{
title:'吃饭',
checked:true
},
{
title:'跑步',
checked:false
},
{
title:'上班',
checked:false
},
{
title:'睡觉',
checked:true
},
],
}
}页面分为顶部的输入框（input）和下面的 待办事项列表 和已办事项列表；在render中的return中编写（jsx）;
render(){
return(
<div>
<header>TodoList: <input> </header>
<h2>待办事项</h2>
<hr>
<ul>
{/* 多个li，后面会循环输出 */}
<li>
<input> -- <button>删除</button>
</li>
</ul>
<h2>已完成事项</h2>
<hr>
<ul>
{/* 多个li，后面会循环输出 */}
<li>
<input> -- <button>删除</button>
</li>
</ul>
</div>
);
}在index.js下，引入ToDoList组件
import ToDoList from './components/ToDoList';
然后挂在组件ToDoList
import React from 'react';
import ReactDOM from 'react-dom';
import './index.css';
import App from './App';
import * as serviceWorker from './serviceWorker';
import ToDoList from './components/ToDoList';
ReactDOM.render(
<react.strictmode>
{/* 此处是ToDoList组件 */}
<todolist></todolist>
</react.strictmode>,
document.getElementById('root')
);
// If you want your app to work offline and load faster, you can change
// unregister() to register() below. Note this comes with some pitfalls.
// Learn more about service workers: https://bit.ly/CRA-PWA
serviceWorker.unregister();简陋渲染效果如下：
图3.1
添加待办事项
（1）使用ref属性，获取input输入值：
在input标签上设置属性ref="inputToDo",然后在方法中可以通过 this.refs.inputToDo.value获取输入值；
（2）添加键盘事件，监听输入变化，当输入enter时，添加待办事项；
使用onKeyUp(键盘弹起)/onKeyDown(键盘按下)事件来监听键盘变化。当键盘变化后，触发添加函数，将输入值添加到待办事项中；代码如下：
jsx:
<header>TodoList: <input> </header>
addToDo函数：
addToDo = (event) => {
console.log(event.keyCode);
if(event.keyCode === 13)
{
let tempList = this.state.list;
tempList.push({
title:this.refs.inputToDo.value,
checked:false,
});
this.setState({
list:tempList,
});
this.refs.inputToDo.value = '';
}
}（3）在constructor中使用bind绑定addToDo,这一步是必须的，否则方法不能执行，所有的方法都需要像这样绑定；
this.addToDo = this.addToDo.bind(this);
图3.2
效果：
视频3.1
输出待办事项和已办事项
使用map方法，循环遍历数组，输出每组数据；代码如下：
checked = {value.checked}表示复选框是否打勾，onChange事件触发一个改变事项状态的方法，index是数组的索引，该方法在下文实现；
效果：
图3.3
待办和已办互相转换
这一步的思路也很简单，其实就是在触发checkbox的onChange事件时，将某一个事项的checked值变为相反的值（true->false/false->true）,所以onChange后的方法需要传入数组的索引值，具体实现代码如下：
jsx
<input> {value.title}-- <button>删除</button>checkboxChange
checkboxChange = (index) => {
let tempList = this.state.list;
tempList[index].checked = !tempList[index].checked;
this.setState({
list:tempList,
});
}效果：
视频3.2
删除事项
删除事项比较简单了，思路也是类似的，在button上添加onClick按钮，触发删除事件，传入参数index,然后根据index，使用数组的splice函数，删除某一待办事项。
arrayA.splice(index,n)
该方法第一个参数是数组中的元素位置，第二个参数是从index开始删除多少个元素。
具体实现如下：
jsx
removeToDo
removeToDo = (index) => {
let tempList = this.state.list;
tempList.splice(index,1);
this.setState({
list:tempList,
});
}效果：即为开篇展示的效果
样式随便写了一下，不太好看，这里也把代码丢上来吧；
index.css
.list{
padding: 10px;
}
.list li{
line-height: 40px;
margin-left: 30px;
}
.title{
height: 44px;
line-height: 44px;
text-align: center;
background: #000;
color:#fff;
}
.title input{
height: 40px;
}
.container{
width: 800px;
height: 1000px;
margin-left: auto;
margin-right: auto;
background-color: #D0D0D0;
border: #fff solid 1px;
border-radius: 5px;
}
.container h2{
margin-left: 20px;
}
.del-btn {
float: right;
margin-right: 30px;
}引入样式
在ToDoList.jsx中按如下代码引入index.css
import '../assets/index.css';
视频3.3：整体效果展示
//导入React相关依赖
import React from 'react';
import '../assets/index.css';
//创建一个组件
class ToDoList extends React.Component{
//构造函数
constructor(props){
super(props);
//this是父组件（类）的一个实例，实例就类似于java里的一个类，创建了这个类型的一个对象，这个对象就是实例
this.state = {
//this.state里可以写一些初始化的数据
list:[
{
title:'吃饭',
checked:true
},
{
title:'跑步',
checked:false
},
{
title:'上班',
checked:false
},
{
title:'睡觉',
checked:true
},
],
}
this.addToDo = this.addToDo.bind(this);
this.checkboxChange = this.checkboxChange.bind(this);
}
addToDo = (event) => {
console.log(event.keyCode);
if(event.keyCode === 13)
{
let tempList = this.state.list;
tempList.push({
title:this.refs.inputToDo.value,
checked:false,
});
this.setState({
list:tempList,
});
this.refs.inputToDo.value = '';
}
}
checkboxChange = (index) => {
let tempList = this.state.list;
tempList[index].checked = !tempList[index].checked;
this.setState({
list:tempList,
});
}
removeToDo = (index) => {
let tempList = this.state.list;
tempList.splice(index,1);
this.setState({
list:tempList,
});
}
//render渲染虚拟DOM
render(){
return(
<header>TodoList: <input> </header>
待办事项
{/* 多个li，后面会循环输出 */}
{
this.state.list.map((value,index)=>{
if(!value.checked)
{
return (
-
{value.title}
);
}
})
}
已完成事项
{/* 多个li，后面会循环输出 */}
{
this.state.list.map((value,index)=>{
if(value.checked)
{
return (
-
{value.title}
);
}
})
}
);
}
}
//输出组件,使得该组件可以被其他组件调用
export default ToDoList;index.css
.red{
color:red;
}
.list{
padding: 10px;
}
.list li{
line-height: 40px;
margin-left: 30px;
}
.title{
height: 44px;
line-height: 44px;
text-align: center;
background: #000;
color:#fff;
}
.title input{
height: 40px;
}
.container{
width: 800px;
height: 1000px;
margin-left: auto;
margin-right: auto;
background-color: #D0D0D0;
border: #fff solid 1px;
border-radius: 5px;
}
.container h2{
margin-left: 20px;
}
.del-btn {
float: right;
margin-right: 30px;
}index.js
import React from 'react';
import ReactDOM from 'react-dom';
import './index.css';
import App from './App';
import * as serviceWorker from './serviceWorker';
import ToDoList from './components/ToDoList';
ReactDOM.render(
<react.strictmode>
{/* <app></app> */}
<todolist></todolist>
</react.strictmode>,
document.getElementById('root')
);
// If you want your app to work offline and load faster, you can change
// unregister() to register() below. Note this comes with some pitfalls.
// Learn more about service workers: https://bit.ly/CRA-PWA
serviceWorker.unregister();结语就算了吧，好困，睡了。
写博客费时间啊，大家要是看到有啥不对的地方，麻烦联系我修改哈，我水平太有限了，谢谢大佬们了。
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