I thought I should add some new fun features to our sample extension to explore a few more things that can be done with Chrome extensions. I was curious about badges because they seem like an interesting tool to communicate changes in the state of our extension to our users.

About badges

Badges appear over the Browser Action Icon and include a short text.

The text can include a number of characters, but the badge will only show the amount that fits in that tiny space (the docs say around 4, but I could fit a maximum of 6). The characters that don’t fit won’t be visible, so try to keep your badge text short.

To create a badge all we need to do is set the text, like so:

chrome.browserAction.setBadgeText({ tabId: myTabId, text: 'grr' });
// or to add it to all tabs:
chrome.browserAction.setBadgeText({ text: 'grr' });

• The tabId is optional, but when included, the text specified for the badge will only be visible when that particular tab is active.
• The text is optional too, but the badge won’t be visible if we don’t include it.

So, to hide the badge all we need to do is set the text for that particular tab to null:

chrome.browserAction.setBadgeText({ tabId: myTabId, text: null });
// or, the shorter version:
chrome.browserAction.setBadgeText({ tabId: myTabId });
// or to remove it from all tabs:
chrome.browserAction.setBadgeText({ });

For extra customization, we can also change the background color of the badge (the default is blue):

chrome.browserAction.setBadgeBackgroundColor({ color: '# F00' }, () => {
    // callback
});

Updating our sample extension

You see, 🐶 Acho gets impatient whenever a new page or tab is loaded and we don’t ask him about it right away (I mean, it’s his job!). So we’ll give him a tool to express himself:

• When a new tab is created, or the active tab gets updated, Acho will let us know he’s ready to work by creating a badge.
• After his job is done, the badge will disappear.

Here’s how it will look:

So first, we’ll update the Acho class acho.js to give him the ability to growl and be quiet:

// acho.js
class Acho {

    growl = () => {
        chrome.browserAction.setBadgeBackgroundColor({ color: '# F00' }, () => {
            chrome.browserAction.setBadgeText({ text: 'grr' });
        });
    }

    quiet = () => {
        chrome.browserAction.setBadgeText({});
    }
}

Then we’ll listen for the tabs.onCreated and tabs.onUpdated events in our background.js, and when they’re fired we’ll let Acho growl using the growl method we just added:

// background.js
chrome.tabs.onUpdated.addListener((tabId, changeInfo, tab) => {
    new Acho().growl();
});

chrome.tabs.onCreated.addListener(tab => {
    new Acho().growl();
});

And finally, we’ll ask Acho to be quiet when he fulfills his job. This must be done both in the background.js file and the popup.js file since Acho can do his job through the browser action (popup) or a command handled in the background script.

In the background script, we must add a new line at the end of our barkTitle method. So, once the notification is sent, we can remove the badge:

// background.js
const barkTitle = async () => {
    const acho = new Acho();
    const tab = await acho.getActiveTab();

    chrome.tabs.sendMessage(tab.id, {
        tabTitle: tab.title
    });

    await PageService.savePage(tab.title, tab.url);

    acho.quiet();   // 👈
}

In the popup.js, we will remove the notification after loading all the info in the popup:

// popup.js
document.addEventListener('DOMContentLoaded', async () => {
    
    const dialogBox = document.getElementById('dialog-box');
    
    const acho = new Acho();
    const tab = await acho.getActiveTab();
    const bark = acho.getBarkedTitle(tab.title);

    dialogBox.innerHTML = bark;
    
    // Store page.
    await PageService.savePage(tab.title, tab.url);

    // Display history.
    await displayPages();

    // Clear history
    const clearHistoryBtn = document.getElementById('clear-history');
    clearHistoryBtn.onclick = async () => {
        await PageService.clearPages();
        await displayPages();
    };

    acho.quiet();   // 👈
});

Done!

That’s it! We learned how to add a badge, hide it and change its color, and now Acho can express his frustration when we don’t let him fulfill his purpose 😂.

The repo

You can find this and all of the examples of this series in my repo:

This post is also available on DEV.