How to implement todolist using react

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.

1. Example display and function introduction

1.1 Example display

Video 1.1

1.2 Function introduction

• Add a to-do item, press the enter key to confirm, and clear the input box at the same time;
• You can switch between to-do and done items by checking whether the checkbox is checked ;
• Click Delete to delete items

2. Preparation work

2.1 Environment configuration reminder

Before preparation: This article assumes development The environment has been configured, including:

• Node.js has been installed;
• cnpm has been installed; npm install -g cnpm --registry=https://registry. npm.taobao.org
• The scaffolding tool has been installed; npm install -g create-react-app / cnpm install -g create-react-app

Note: First time An error that prohibits running scripts will occur when configuring the scaffolding. For the solution, click: https://www.php.cn/link/e543789a8d5b6a0e6b2f2a804d207e8d

2.2 Create a new React project

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.

2.3 File classification

• Create a new components folder in the src directory to place the components you create;
• Create a new assets file in the src directory to add it To prevent static resources such as css files and image files;

As shown in Figure 2.5:

Figure 2.5

3. Implementation process

3.1 Create component ToDoList

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;

The function of each part of the component is briefly described in the comments. A basic component generally includes the above parts:

• import导入的依赖;
• 组件（class XXX extends React,Component）;
• 构造函数constructor;
• render函数；
• export输出组件；

3.2 功能实现与解析

1.初始化数据

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
                },
            ],
        }
    }

2.编写页面布局

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 id="待办事项">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 id="已完成事项">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>
        );
    }

 3.挂载到根节点下

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

3.功能实现

• 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：

                    {/* 多个li，后面会循环输出 */}                     {                         this.state.list.map((value,index)=>{ 　　　　　　　　　　　　　　　　{/*checked为false表示待办*/}                             if(!value.checked)                             {                                 return (                                     
• 　　　　　　　　　　　　　　　　　　　　　　　　　{/* */}                                         <input> {value.title}-- <button>删除</button>                                     
                                );                             }                         })                     }  

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

        {value.title}        -- 删除  

 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 

3.3 编写样式

 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';

3.4 整体效果

 

视频3.3：整体效果展示

四、整体代码

• ToDoList.jsx

//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(
            <div>
                 <header>TodoList: 　<input> </header>
                    <div>
                        <h2 id="待办事项">待办事项</h2>

                        <hr>

                        <ul>
                            {/* 多个li，后面会循环输出 */}
                            {
                                this.state.list.map((value,index)=>{
                                    if(!value.checked)
                                    {
                                        return (
                                            <li>
                                                <input> {value.title}
                                                <button>删除</button>
                                            </li>
                                        );
                                    }

                                })
                            }

                        </ul>
                        <h2 id="已完成事项">已完成事项</h2>

                        <hr>
                        <ul>
                            {/* 多个li，后面会循环输出 */}
                            {
                                this.state.list.map((value,index)=>{
                                    if(value.checked)
                                    {
                                        return (
                                            <li>
                                                <input> {value.title}
                                                <button>删除</button>
                                            </li>
                                        );
                                    }
                                })
                            }
                        </ul>
                 </div>
            </div>
        );
    }

}


//输出组件,使得该组件可以被其他组件调用
export default ToDoList;

View Code

• 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();

五、结语

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。

 推荐学习：《react视频教程》

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