We keep our book up to date with recent libraries and packages.

The section below is a preview of Browser Extension Book. To read the full text, you will need to purchase the book.

In Chapter 1, you will end up with the codebase in the 1-end folder.

We will cover the following topics in this chapter:

• Understanding browser extensions
  
• Setting up your development environment
  
• Building basic extension
  
• Loading and Testing the Extension

Understanding browser extensions link

Browser extensions are small software programs that extend the functionality of web browsers. They allow users to customize their browsing experience by adding new features, modifying existing ones, or enhancing browser capabilities.

Core concepts link

1.1. Browser compatibility

Browser extensions are typically designed for specific web browsers such as Google Chrome, Mozilla Firefox, Microsoft Edge, or Safari. Each browser has its own extension architecture and API (Application Programming Interface) for developing extensions.

1.2. Content scripts

Content scripts are JavaScript files that can be injected into web pages to modify their behavior or appearance. They have access to the DOM (Document Object Model) of the page and can interact with it dynamically. Content scripts are often used to add functionality to specific web pages or to enhance the user experience.

Example of a content script:

// content.js
console.log("This is a content script!");

To include a content script in your extension, you need to specify it in the manifest file.

1.3. Background scripts

Background scripts run in the background of the browser and handle events or perform tasks that don't require direct interaction with web pages. They can listen for browser events, communicate with content scripts, and manage extension state. Background scripts are useful for tasks such as handling browser actions, managing data storage, or performing periodic tasks.

Example of a background script:

// background.js
console.log("This is a background script!");

Background scripts are declared in the manifest file under the background field.

1.4. User interface (UI)

Extensions often include a user interface for configuration or interaction. This can include browser action buttons, context menus, options pages, or pop-up windows that allow users to control the extension's behavior. The UI components of an extension are created using HTML, CSS, and JavaScript.

Example of a browser action button:

{
  "manifest_version": 3,
  "name": "My Extension",
  "version": "1.0",
  "action": {
    "default_popup": "popup.html",
    "default_icon": {
      "16": "icon-16.png",
      "48": "icon-48.png",
      "128": "icon-128.png"
    }
  },
  ...
}

1.5. Permissions

Extensions may require certain permissions to access browser features or interact with web pages. These permissions are specified in the extension's manifest file and must be explicitly granted by the user during installation. Common permissions include accessing tabs, reading and modifying the browser's history, or interacting with external websites.

Example of requesting permissions:

{
  "manifest_version": 3,
  "name": "My Extension",
  "version": "1.0",
  "permissions": [
    "tabs",
    "storage",
    "activeTab"
  ],
  ...
}

1.6. Manifest file

The manifest file is a JSON (JavaScript Object Notation) file that provides metadata about the extension, including its name, version, permissions, content scripts, background scripts, and other important details. It serves as the blueprint for the extension's behavior and functionality.

Example of a manifest file:

{
  "manifest_version": 3,
  "name": "My Extension",
  "version": "1.0",
  "description": "This is a description of my extension.",
  "permissions": [
    "tabs",
    "storage"
  ],
  "action": {
    "default_popup": "popup.html",
    "default_icon": {
      "16": "icon-16.png",
      "48": "icon-48.png",
      "128": "icon-128.png"
    }
  },
  "background": {
    "service_worker": "background.js"
  },
  "content_scripts": [
    {
      "matches": ["<all_urls>"],
      "js": ["content.js"]
    }
  ],
  ...
}

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We keep our book up to date with recent libraries and packages.