02.15 React State - User List in one component (class components)
Tags: javascript, react, tutorial, webdev
Published: 2022-10-26 07:46:02

App preview:
![The way the app will look like](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/3iclevv5xusy8ms67vym.gif)



Project files:
![An image of project file structure](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/jvtxebehqkcqonm8qci8.png)



<hr/>
src/App.js
```react
import React from 'react';
import './App.css'

class App extends React.Component{
  constructor(){
    super();
    this.state = {
      users: [],
      newUserName: '',
      newUserEmail: '',
    }
  }

  //we use componentDidMount for the side effect 
  //...of populating the initial component state
  componentDidMount(){
    this.setState({ users: [
      {
        name: "Jane Doe",
        email: "jane.doe@gmail.com"
      },
      {
        name: "Joe Shmoe",
        email: "joe.shmoe@gmail.com"
      }
    ]})
  }

  handleNameInputChange(event){
    const inputValue = event.currentTarget.value;
    this.setState({newUserName: inputValue})
  }

  handleEmailInputChange(event){
    const inputValue = event.currentTarget.value;
    this.setState({newUserEmail: inputValue})
  }

  handleFormSubmit(event){
      event.preventDefault(); //prevent page refresh
      const newUser = {
          name: this.state.newUserName,
          email: this.state.newUserEmail,
      }
      this.updateUsersList(newUser);
  }

  updateUsersList =(newUser) => {
    this.setState((previousState)=>{
      return {users: [
        ...previousState.users, 
        newUser
      ]}
    });
  }


  render(){

    return (
      <div className="App" >
        <h1>App.js</h1>

        <div>
          <form className="user-add-form" onSubmit={(event)=>{this.handleFormSubmit(event)}} >
            <label htmlFor="name">Name:</label>
            <input 
                type="text" 
                name="name" 
                onChange={(event)=>{this.handleNameInputChange(event)}}
            />

            <label htmlFor="emai">Email:</label>
            <input 
                type="email" 
                name="email"
                onChange={(event)=>{this.handleEmailInputChange(event)}}
            />

            <input type="submit" value="Add New User!"/>
          </form>  
        </div>
        <br/>
        <button onClick={()=>{console.log(this.state.users)}}>Log users to console!</button>


        <div>
          {
              this.state.users.map((user, index) => {
                  return(
                    //note: react uses keys as a way to identify an element of the same type among its siblings during re-renders
                    <div key={user.email}>
                      <br/>
                      <div><span>{index +1 }. </span><span>{user.name}</span></div>
                      <div><span>{user.email}</span></div>
                    </div>
                  ) 
              }) 
          }
          
        </div>
      </div>
    );
  }
}

export default App;
```
<hr/>
src/App.css
```css
.App{
    background-color: lightskyblue;
    padding: 20px 10px;
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
}
```