A simple component before hooks

SimpleComponent.js

import React, { PureComponent, Fragment } from 'react'

export default class SimpleComponent extends PureComponent {

  constructor(props){
    super(props)
    this.state = { counter: 0 }
  }
  
  handleOnClick = e => {
    e.preventDefault()
    const { counter } = this.state
    this.setState({ counter: counter + 1 })
  }
  
  render = () => {
    const { counter } = this.state
    return (
      <Fragment>
        <h1>Counter: {counter} </h1>
        <button onClick={e => this.handleOnClick(e)}> Click me </button>
      </Fragment>
    )
  }
}