How to use react-native-dotenv - 2 common examples

connect(accessToken: string, shapeshiftAccessToken?: string) {
    this.stop();
    this.tokens = {
      accessToken,
      shapeshiftAccessToken,
    };
    try {
      this.apiConfig = buildAPIConfig(accessToken);
      if (!!shapeshiftAccessToken
        && shapeshiftAccessToken !== '') {
        this.apiConfig.headers = {
          ...this.apiConfig.headers,
          token: shapeshiftAccessToken,
        };
      }
      const wsUrl = EXCHANGE_URL
        .replace(/(https:\/\/)/gi, 'wss://')
        .replace(/(http:\/\/)/gi, 'ws://');
      this.io = new SocketIO(`${wsUrl}:443`, {
        transports: ['websocket'],
        query: {
          token: accessToken,
        },
      });

      this.io.on('disconnect', () => {
        this.setConnected(false);
      });
      this.io.on('error', () => {
        this.setConnected(false);
      });
      this.io.on('connect', () => {

const CONFIG = {
  apiKey: FIREBASE_API_KEY,
  authDomain: FIREBASE_AUTH_DOMAIN,
  databaseURL: FIREBASE_DATABASE_URL,
  projectId: FIREBASE_PROJECT_ID,
  storageBucket: FIREBASE_STORAGE_BUCKET,
  messagingSenderId: FIREBASE_MESSAGING_SENDER_ID,
};

/**
 * NOTE: Condition prevents repeated Firebase initialisation,
 * which can occur during web version hot reload in development mode.
 * Also forbids initialisation in case when firebase .env vars
 * are not set (and left empty).
 */
if (!firebase.apps.length && FIREBASE_API_KEY.length > 0) {
  firebase.initializeApp(CONFIG);
}