Answers for "state in class component"

how to write statefull class in react

import React, {Component} from 'react'

class Pigeons extends Component {
  constructor() {
    super()
    this.state = {
      pigeons: []
    }
  }
  render() {
    return (
      <div>
        <p>Look at all the pigeons spotted today!</p>
        <ul>
          {this.state.pigeons.map(pigeonURL => {
            return <li><img src={pigeonURL} /></li>
          })}
        </ul>
      </div>
    )
  }
}

class component react using state

import React, {Component} from 'react';
import './App.css';
import IconBar from './components/icon-bar';
import Events from './components/events';

class App() extends Component {
  constructor(props) {
        super(props)
        this.state = {
            mode: null
        }
        this.updateMode = this.updateMode.bind(this);
    }

  updateMode = (newMode) => {

      this.setState({mode: newMode});
  }


  return (
    <div className="App">
      <h1 className="Title">ENAKS</h1>
      <IconBar onUpdateMode={this.updateMode}  mode={this.state.mode} />
      <Events />
  <div className="mainModeFrame"><p1>{this.state.mode}</p1></div>
    </div>
  );
}

export default App;
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set state

class App extends React.Component {

state = { count: 0 }

handleIncrement = () => {
  this.setState({ count: this.state.count + 1 })
}

handleDecrement = () => {
  this.setState({ count: this.state.count - 1 })
}
  render() {
    return (
      <div>
        <div>
          {this.state.count}
        </div>
        <button onClick={this.handleIncrement}>Increment by 1</button>
        <button onClick={this.handleDecrement}>Decrement by 1</button>
      </div>
    )
  }
}

state react

class Example extends React.Component {
  constructor(props) {
    super(props);
    this.state = {
      count: 0
    };
  }

  render() {
    return (
      <div>
        <p>You clicked {this.state.count} times</p>
        <button onClick={() => this.setState({ count: this.state.count + 1 })}>
          Click me
        </button>
      </div>
    );
  }
}

react lifecycle example

class Test extends React.Component {
  constructor() {
    console.log('Constructor')
    super();
    this.state = {
      count: 0
    };
  }

  componentDidMount() {
    console.log("component did mount");
  }
  componentDidUpdate() {
    console.log("component did update");
  }

  onClick = () => {
    this.setState({ count: this.state.count + 1 });
  };
  render() {
    console.log("render");
    return (
      <div>
        Hello Test
        <button onClick={this.onClick}>
      		{this.state.count}
		</button>
      </div>
    );
  }
}


//--for first time
//Constructor
//render
//component did mount
//--for any update
//render
//component did update

react lifecycle hooks

class ActivityItem extends React.Component {
  render() {
    const { activity } = this.props;

    return (
      <div className='item'>
        <div className={'avatar'}>
          <img
            alt='avatar'
            src={activity.actor.avatar_url} />
        </div>

        <span className={'time'}>
          {moment(activity.created_at).fromNow()}
        </span>
        
        <p>{activity.actor.display_login} {activity.payload.action}</p>
        <div className={'right'}>
          {activity.repo.name}
        </div>
      </div>
    )
  }
}