Building Extensions for the Modern Browsers...

BITS - GOA | 14th January 2018

Santosh Viswanatham

Javascript Engineer at Gaian Solutions India Pvt Ltd

Mozilla Tech Speaker

Mozilla Rep

Senior Systems Engineer at Infosys Ltd (Previously)

 

@isantoshv | viswanathamsantosh.github.io |viswanathamsantosh@gmail.com

  • Browser Add-ons
  • WebExtensions
  • Anatomy of WebExtensions
  • Extension API's
  • Contribution opportunities

Agenda

Browser Add-ons extend and modify the functionality of the browser.

Browser Add-ons?

Firefox is the most customizable browser!

1 Million+ addons downloaded everyday

150million+ Add-ons used everyday

45+ percentage of users use at least one Add-on

WebExtensions

A cross-browser system for developing browser add-ons

  • Uses standard HTML, CSS and JS
  • e10s compatible (multiprocess)
  • Few changes and you can run it on Chrome, Edge and Opera
  • Documentations from multiple resources.

Why WebExtensions?

Few WebExtension API's

Anatomy/Architecture of WebExtensions

manifest.json

{
  "manifest_version": 2,
  "name": "inShorts in dark",
  "version": "2.0.1",
  "homepage_url": "https://github.com/viswanathamsantosh/inshorts",
  "description": "Read your favourite news on inShorts by dimming the light right away on your browser.",
  "icons": {
    "48": "icons/icon-48.png",
    "96": "icons/icon-96.png"
  },
  "permissions": [
    "activeTab",
    "tabs"
  ],
  "browser_action": {
  "browser_style": true,
  "default_icon": {
    "19": "icons/icon-19.png",
    "38": "icons/icon-38.png"
  },
  "default_title": "Turn on or off"
  },
  "background": {
    "scripts": ["background.js"]
  }
}

Background scripts

  • Loaded as soon as the extension is loaded

  • Stay loaded until the extension is disabled or uninstalled

  • You can use any of the WebExtension APIs in the script

"background": {
  "scripts": ["background-script.js"]
}

Content Scripts

  • Similar to loading normal scripts in the page

  • Can access DOM structure and use a small subset of the WebExtension APIs

  • Make cross-domain XHR requests

  • Exchange messages with their background scripts and can in this way indirectly access all the WebExtension APIs

"content_scripts": [
  {
    "matches": ["*://*.mozilla.org/*"],
    "js": ["jquery.js", "content-script.js"]
  }
]

Browser action

  • Used to add button to browser toolbar
  • Use this when your add-on's features are applicable to all websites else use Page action instead.
"browser_action": {
  "default_icon": {
    "19": "button/geo-19.png",
    "38": "button/geo-38.png"
  },
  "default_title": "Whereami?",
  "default_popup": "popup/choose_beast.html"
}
browser.browserAction.onClicked.addListener(handleClick);

Page action

  • Used to add button to address toolbar
  • Use this when your add-on's features are specific to a particular website.
"page_action": {
  "default_icon": {
    "19": "button/geo-19.png",
    "38": "button/geo-38.png"
  },
  "default_title": "Whereami?",
  "default_popup": "popup/choose_beast.html"
}
browser.pageAction.onClicked.addListener(handleClick);

Resources such as images, HTML, CSS, and JavaScript that you include in the extension.

WebExtension API's

webRequest API

Sequence of events

var target = "https://developer.mozilla.org/*";

/*
e.g.
"https://developer.mozilla.org/en-US/"
200

or:

"https://developer.mozilla.org/en-US/xfgkdkjdfhs"
404
*/
function logResponse(responseDetails) {
  console.log(responseDetails.url);
  console.log(responseDetails.statusCode);
}

browser.webRequest.onCompleted.addListener(
  logResponse,
  {urls: [target]}
);

Example:

Notifications API

 browser.notifications.create(cakeNotification, {
    "type": "basic",
    "iconUrl": browser.extension.getURL("icons/cake-96.png"),
    "title": "Time for cake!",
    "message": "Something something cake"
  });

Alarms API

const delayInMinutes = 5;

browser.alarms.create({
  delayInMinutes
});

Tabs API

function onCreated(tab) {
  console.log(`Created new tab: ${tab.id}`)
}

function onError(error) {
  console.log(`Error: ${error}`);
}

browser.browserAction.onClicked.addListener(function() {
  var creating = browser.tabs.create({
    url:"https://example.org"
  });
  creating.then(onCreated, onError);
});
function onCreated(windowInfo) {
  console.log(`Created window: ${windowInfo.id}`);
}

function onError(error) {
  console.log(`Error: ${error}`);
}

browser.browserAction.onClicked.addListener((tab) => {
  var creating = browser.windows.create({
    url: ["https://developer.mozilla.org",
          "https://addons.mozilla.org"]
  });
  creating.then(onCreated, onError);
});

Windows API

Runtime API

// content-script.js

function handleResponse(message) {
  console.log(`background script sent a response: ${message.response}`);
}

function handleError(error) {
  console.log(`Error: ${error}`);
}

function sendMessage(e) {
  var sending = browser.runtime.sendMessage({content: "message from the content script"});
  sending.then(handleResponse, handleError);  
}

window.addEventListener("click", sendMessage);

// background-script.js

function handleMessage(request, sender, sendResponse) {
  console.log(`content script sent a message: ${request.content}`);
  sendResponse({response: "response from background script"});
}

browser.runtime.onMessage.addListener(handleMessage);

web-ext CLI

A command line tool to help build, run, and test WebExtensions.

npm install --global web-ext

Few Commands

  • run
    • Run the extension
  • lint
    • Validate the extension source
  • sign
    • Sign the extension so it can be installed in Firefox
  • build
    • Create an extension package from source
  • docs
    • Open the web-ext documentation in a browser
use --help on the command line, such as web-ext build --help

Debugging your add-on

Publishing your Add-on

Not only this...

You can be a content reviewer!

or an Addon Reviewer!

Themes in Firefox!

Code Contribution!

AMO(add-ons frontend and server)

Links:

Need help?

IRC Channels: #webextensions, #extdev, #addons

Mailing List: https://mail.mozilla.org/listinfo/dev-addons

Telegram: @addonschat

Questions?

Santosh Viswanatham | @isantoshv | viswanathamsantosh@gmail.com

Slides: https://slides.com/isantoshv/fx-addons-bits

Building Extensions for the Modern Browsers

By Santosh Viswanatham

Building Extensions for the Modern Browsers

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