Flowtype fundamentals with React.js

BasicComponent.js

// @flow
import React from 'react'

type Props = {
  foo: number,
  bar: string,
  disabled: boolean,
  children?: React.Element<any>
}

type State = {
  foo: boolean
}

class A extends React.Component<Props, State> {
  state = {
    foo: false
  }
  
  render () {
    const { foo } = this.state
    return (
      <div>
        <h1>Title</h1>
        <span>Component State: {foo}</span>
        {this.props.children}
      </div>
    )
  }
  
}