Adding listeners to the client-side script

After installing Firebase and initializing the data in the Firebase Realtime Database, append the following code to your public/script.js file:

    /**
     * Initialize a new database with the firebase.database 
    constructor
     */
    const database = firebase.database()

    /**
     * database.ref returns a reference to a key in the 
    realtime database.
     * This reference comes with a listener to read the value 
    for the first time, and execute some action everytime a 
    value is received
     */
    const temperatureListener = database.ref('temperature')

    temperatureListener.on('value', data => {
      /**
       * The contents of the listener are pretty much the
     same as the listeners in our previous chapters. The only     difference being that the value
       * of the data being read has...