Example of using class fields

class-fields.js

// Use class fields!
// https://github.com/tc39/proposal-class-fields

// Here's what you might be doing today...
class A extends B {
  constructor(...args) {
    super(...args)
    this.foo = 'bar'
    this.foobar = `${this.foo}bar`
  }
}

// this has the exact same semantics as the above example!
class A extends B {
  foo = 'bar'
  foobar = `${this.foo}bar`
}

// Here's a more practical react example:
const incrementCount = ({count}) => ({count: count + 1})

class Counter extends React.Component {
  static defaultProps = {initialCount: 0}
  state = {
    count: this.props.initialCount
  }
  handleClick = () => this.setState(incrementCount)
  render() {
    return (
      <button onClick={this.handleClick}>
        {this.state.count}
      </button>
    )
  }
}
// Photo by Sandro Katalina on Unsplash
// example by @kentcdodds