The Code (Cont.): HTML
https://ajax.googleapis.com/ajax/libs/jquery/4.0.0/jquery.min.js
There are several ways to start using jQuery on your web site:

  • Download the jQuery library from jQuery.com.
  • Include jQuery from a CDN, which is used by this application.

Instead of downloading the jQuery, you can include jQuery from a CDN (Content Delivery Network) such as Google by using the following command:
<scrip src="jQuery address"> </script>
https://www.gstatic.com/firebasejs/10.14.1/firebase-app-compat.js
The program does not work for 
https://www.gstatic.com/firebasejs/10.14.1/firebase-app.js
because of the problem of backward compatibility. Instead of downgrading to SDK 8, use the above backward compatible import. This address shows the Firebase SDK (software development kit) used by this application. Gstatic.com is a Web domain owned and used by Google for accessing the Gstatic server: a server where Google hosts its static content like CSS, JavaScript code, and images. The reason why Google hosts its content on that specific server is to reduce bandwidth usage and deliver the content faster.
The available Firebase JS SDKs (from the CDN) can be found from here.
Other than CDN, you may use npm (JavaScript package manager), which is a package manager for the JavaScript programming language maintained by npm, Inc., a subsidiary of GitHub. You can run the following command to install the latest Firebase SDK:
shell> npm install firebase
<!DOCTYPE html>
<html lang="en">
 <head>
  <script src=
   "https://ajax.googleapis.com/ajax/libs/jquery/4.0.0/jquery.min.js">
  </script>
  <script src=
   "https://www.gstatic.com/firebasejs/10.14.1/firebase-app-compat.js">
  </script>
  <script src=
   "https://www.gstatic.com/firebasejs/10.14.1/firebase-database-compat.js">
  </script>
  <script src=
   "https://www.gstatic.com/firebasejs/10.14.1/firebase-analytics-compat.js">
  </script>
  <title>Managing Firebase data</title>
 </head>

 <body>
  <center>Managing Firebase Data</center>
  <form id="contact">
   ID: <input type="text" size="3" id="ID" value="1" />
   Name: <input type="text" size="30" id="name" value="Poke Mon" />
   Email: <input type="email" size="30" id="email" value="poke@example.com" />
   <p id="result">[result]</p>

   <button type="submit" onClick="addUser( ); return false;">Add a user
   </button>   (required: ID, name, email)

   <button type="submit" onClick="showUser( ); return false;">Show a user
   </button>   (required: ID)

   <button type="submit" onClick="showAll( ); return false;">Show all users
   </button>

   <button type="submit" onClick="deleteUser( ); return false;">Delete a user
   </button>   (required: ID)

   <button type="submit" onClick="deleteDB( ); return false;">Delete the database
   </button>

   <button type="submit" onClick="updateUser( ); return false;">Update a user
   </button>   (required: ID)

   <button type="reset">Reset</button>
  </form>





      Q: Why did the clock get kicked out of the classroom?    
      A: It tocked too much…