Step 1: Create a folder on your computer and call it JSClock. Create a manifest file (text file) inside the folder and call it manifest.json. Add the following contents to the file
"name": "World Clock",
"description": "World Clock showing Time of 12 countries",
Note: If you are using any information from an external website, such as Google or Flickr, you also need to provide permission to the environments in which you’ll work. That’s done by adding the permission info to the manifest as follows:
"permissions": ["http://*.google.com/", "http://api.flickr.com/"]
Anyways for this example, we do not need to add the permission info. So leave the manifest as it is. As you will observe, the manifest file provides browser actions (for UI) to load a HTML page and an icon. So let’s create them.
Step 2: Add an icon to the folder. I downloaded a clock icon file from here and rename it as clock.ico
Your extension is ready. I told you it’s easy! You can download the entire folder here (uncompress it before using).
Installing the Extension
Step 4: All you have to do now is load the extension in Chrome. Open Chrome, click on the Tools icon ( )in the top-right corner of your browser > Select Tools > Extensions. Click the + Developer Mode to expand it if it is not already expanded.
Click on ‘Load unpacked extension..’ button and browse to the JSClock folder and click ok. If everything is in place, you will be able to view information about the extension in the extensions page as shown below:
Your extension has been installed! To view it, check the World Clock icon next to the address bar in the Chrome toolbar.
Clicking the dropdown brings up the rest of the countries.
If you plan to distribute your extension, the contents of the folder are packaged into a special ZIP file that has a
.crx suffix. Read more on Hosting an extension
IMHO, Developing an extension for Google Chrome is the simplest of all the browsers! Note that I have tested this extension only on Windows, although it should also work on a Mac.