Returning Null - Initial State

App.js

import React, { Component } from 'react';

import Mocktail from './Mocktail';

class App extends Component {

  state = {
    mocktail: ''
  }

  updateMocktail = mocktail => this.setState({ mocktail })

  render() {

    const mocktails = ['Cosmopolitan', 'Mojito', 'Blue Lagoon'];

    return (
      <React.Fragment>
        <header>
          <h1>Select Your Mocktail</h1>
          <nav>
            {
              mocktails.map((mocktail) => {
                return <button 
                  key={mocktail}
                  value={mocktail}
                  type="button"
                  onClick={e => this.updateMocktail(e.target.value)}>{mocktail}</button>
              })
            }
          </nav>
        </header>
        <main>
            <Mocktail mocktail={this.state.mocktail} />
        </main>
      </React.Fragment>
    );
  }
}

export default App;