Counter.js

'use strict';

import React, {Component} from 'react'
import PropTypes from 'prop-types'

class Counter extends Component {
  constructor(props) {
    super(props);
    this.incrementAsync = this.incrementAsync.bind(this);
    this.incrementIfOdd = this.incrementIfOdd.bind(this)
  }

  incrementIfOdd() {
    if (this.props.value % 2 !== 0) {
      this.props.increment()
    }
  }

  incrementAsync() {
    setTimeout(this.props.increment, 1000)
  }

  render() {
    const {value, increment, decrement} = this.props;
    return (
      <p>
        Clicked: {value} times
        {' '}
        <button onClick={increment}>
          +
        </button>
        {' '}
        <button onClick={decrement}>
          -
        </button>
        {' '}
        <button onClick={this.incrementIfOdd}>
          Increment if odd
        </button>
        {' '}
        <button onClick={this.incrementAsync}>
          Increment async
        </button>
      </p>
    )
  }
}

Counter.propTypes = {
  value: PropTypes.number.isRequired,
  increment: PropTypes.func.isRequired,
  decrement: PropTypes.func.isRequired
};

export default Counter