Introduction to using Cloud9


This workshop has been retired and is no longer maintained or recommended.

Cloud9 logo

What is Cloud9?

Cloud9 is a website that lets you program online. Traditionally, all programming was done locally on the computer: you would save your files on your computer and edit them on your computer (with a code editor). Cloud9 allows you to save your files online and edit your files online (Cloud9 also has a code editor). This means all you need to start programming is internet and a browser. No more installing software!

Important: if you're having trouble, checkout the troubleshooting section at the end of the workshop.

Tips And Tricks

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Login with GitHub

First, make sure you have a GitHub account. If you don't have one, follow the guide here.

Now that you have a GitHub account, you can login to Cloud9 with GitHub. Go to and click on the Octocat icon in the top corner as demonstrated below:

Create a New Workspace

To create a new workspace you can either select the create a new workspace option under workspaces, or click the new workspace button at the top right of your screen.

New workspace buttons

Next set your workspace name to html-css-javascript-basics, and your description to Learning to use HTML, CSS, and JavaScript together. Make your workspace public, skip the Clone from Git or Mercurial URL option and set your template to Custom. Finally click the Create Workspace button at the bottom of your page and you should be prompted to this screen.

Using HTML CSS and JavaScript Together in Cloud9

First we will create a new folder. To do this right click the workspace bar on the left and select New Folder. You can name this folder whatever you like.

Next we will be creating an HTML file. To do this hit file on the top left of your screen, hover over the New From Template option, and select HTML file. Now we want to save this file in the new folder we just created. To do this go to File and click Save As. Name your file index.html and save it inside the folder you just created.

Repeat the last step twice more, except this time create a CSS file and a JavaScript file. Name your files style.css and index.js

Now that you have your files set up lets start building. Inside your index.html file in the body element create a button with the attribute id set to alertButton.

<button id="alertButton">Click Me!</button>

To preview you file right click your index.html file in your workspace sidebar to the left and hit Preview. This will open up a new tab with the rendered version of your HTML file.

Adding CSS to Your HTML

Next lets add some style to our button. In your style.css file add the following code

#alertButton {
  background: none;
  border-style: none;
  border: 2px solid black;
  padding: 10px;
  color: black;

#alertButton:hover {
  background-color: black;
  color: white;

CSS Selectors

In CSS, selectors are patterns used to select the element(s) you want to style. If we were to do

button {
  // css goes here

Our CSS would still work, however if we had multiple buttons in our HTML, all those buttons would be styled the same because every button element in our HTML would have the same CSS applied to it. If we want different styles for each button, we can give each button a unique id attribute in HTML. Then when we want to reference that id attribute in our CSS we can do.

#idName {
  // css goes here

Another CSS selector that we encountered is the hover selector seen here.

#alertButton:hover {
  background-color: black;
  color: white;

This basically says that when a mouse hovers over the HTML element with the id alertButton, apply this CSS to that element. You read more about CSS selectors here.

If you look at your preview, you will notice none of the styles were applied to your button. This is because you have to tell your HTML file where to get the CSS from. To do this we will add this code inside the head element of your HTML.

<link rel="stylesheet" href="style.css" type="text/css" />

Basically what this does is link your HTML to your CSS. The value of your href attribute should be the location of your CSS file. Since our CSS file is in the same folder as our HTML all we have to do is set the value of href to the name of our CSS file.

Adding JavaScript to Your HTML

Next lets add some JavaScript. Inside your index.js file add the following code.

var button = document.getElementById('alertButton')

button.onclick = function() {
  alert('Button was pressed')

Understanding the code

In our JavaScript file we start of by creating a variable called button and set it equal to the element in our HTML that has an id of alertButton. Next we declare that when our button is clicked, a function is run that alerts the user with the message "Button was pressed".

If we try testing our code, it wont work yet for the same reason our CSS didn't work at first. We need to tell our HTML file where to get the JavaScript from. To do this, we will add the following code to the end of the body element inside our HTML.

<script type="text/javascript" src="index.js"></script>

This links our HTML and our JavaScript together. The src attribute should be set to the location of our JavaScript file. Since our JavaScript file is in the same folder as our HTML, all we have to do is set the value of src to the name of our JavaScript file.

Go ahead and test your code now.


  • Nothing shows up
    • Try saving the index.html file from File > Save. After that reload the preview.
  • CSS not applying styles to the button
    • Make sure the href attribute of the <link> element in index.html points to a file in the same directory at as index.html called style.css.
    • Make sure you have a CSS file called style.css.
    • Make sure the id attribute of the <button> in index.html is the same as the id being selected in your style.css file (minus the #). ID's ARE case sensitive!
  • JavaScript is not displaying the alert
    • Make sure the src attribute of the <src> element in index.html points to a file in the same directory at as index.html called index.js.
    • Make sure you have a JavaScript file called index.js.
    • Make sure the id attribute of the <button> in index.html is the same as the id being selected in the document.getElementById function in your index.js file (minus the #). ID's ARE case sensitive!


You now know how to:

  • Create a new workspace in Cloud9
  • Work with HTML, CSS, and JavaScript together
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