CODE EXAMPLE FOR JAVASCRIPT

Where to Initialize State in React

class App extends React.Component {
  constructor(props) {
    // Required step: always call the parent class' constructor
    super(props);

    // Set the state directly. Use props if necessary.
    this.state = {
      loggedIn: false,
      currentState: "not-panic"
      someDefaultThing: this.props.whatever
    }
  }

  render() {
    // whatever you like
  }
}