class App extends React.Component {
    constructor() {
        super()
        this.state = {
            isLoggedIn: false
        }
        this.handleClick = this.handleClick.bind(this)
    }

    handleClick() {
        this.setState(prevState => {
            return {
                isLoggedIn: !prevState.isLoggedIn
            }
        })
    }

    render() {
        return (
            <div>
                {this.state.isLoggedIn ? <h1>You are now logged in.</h1> : <h1>You are now logged out.</h1>}
                <button onClick={this.handleClick}>{this.state.isLoggedIn ? <h3>LOG OUT</h3> : <h3>LOG IN</h3>}</button>
            </div>
        )
    }
}