error 'Firebase is not defined' in online IDE (Firebase javascript client script-tag included)

I'm trying to follow the Web Quickstart on Firebase found here but I get stuck on step 2.

I set up a new webpage on Cloud9, using the HTML5 template, with following basic conent:

<html>
    <head>
        <script src="https://cdn.firebase.com/js/client/2.4.0/firebase.js"></script>
    </head>
    <body>
        "Hallo"
        <script>
            var Firebase = require("firebase");
            var myFirebaseRef = new Firebase("https://resplendent-heat-2801.firebaseio.com/");
            myFirebaseRef.set({
              title: "Hello World!",
              author: "Firebase",
              location: {
                city: "San Francisco",
                state: "California",
                zip: 94103
              }
            });
        </script>
    </body>
</html>

If I don't add the line var Firebase = require("firebase"); I get error

'Firebase is not defined'.

If I add the line I get the error:

'uncaught reference error: require is not defined.

I also tried to use a nodeJS template and then run command $ npm install firebase --save in the terminal. Result shows in terminal:

firebase@2.4.0 node_modules/firebase

└── faye-websocket@0.9.3 (websocket-driver@0.5.2)

(so installing firebase seems to work) and then add this page of code but that doesn't make a difference.

How to solve this issue? I do not have the option to install nodeJS locally (working on schoolcomputer).

Solution

Remove the require. Firebase loads correctly from CDN.

Make sure you check security tab and add appropriate rules for write operations.

<html>
    <head>
        <script src="https://cdn.firebase.com/js/client/2.4.0/firebase.js"></script>
    </head>
    <body>
        "Hallo"
        <script>
            //var Firebase = require("firebase");
            var myFirebaseRef = new Firebase("https://resplendent-heat-2801.firebaseio.com/");
            myFirebaseRef.set({
              title: "Hello World!",
              author: "Firebase",
              location: {
                city: "San Francisco",
                state: "California",
                zip: 94103
              }
            });
        </script>
    </body>
</html>