set state in class component react code example

Example 1: 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>
    )
  }
}

Example 2: 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>
    )
  }
}