The final file of the React.js tutorial, which switches between 'day' and 'night' modes

App.js

import React, { Component } from 'react';
import './App.css';

class App extends Component {
  constructor(props) {
    super(props);
    this.state = { skin: 'night' };
    this.changeSkin = this.changeSkin.bind(this);
  }
  
  changeSkin() {
    const newState = this.state;
    this.state.skin === 'night' ? newState.skin = 'day' : newState.skin = 'night';
    this.setState(newState);
}
  
  render() {
    return (
      <div className={this.state.skin}>
        <header className="App-header">
          <p onClick={this.changeSkin} style={{ fontSize: '50px', cursor: 'pointer' }}>Change Skin</p>
        </header>
      </div>
    );
  }
}

export default App;