How can I listen to notifications?

Question

Is there a way for an extension to add a listener to browser notifications, and access it content? I'm trying to use Google Calendar's notifications to fire a custom function.

Answer 1

You can hook the webkitNotifications.createNotification function so that whenever a notification is created you run some particular code.

1. Create a file called notifhook.js:

    (function() {
        // save the original function
        var origCreateNotif = webkitNotifications.createNotification;
   
        // overwrite createNotification with a new function
        webkitNotifications.createNotification = function(img, title, body) {
   
            // call the original notification function
            var result = origCreateNotif.apply(this, arguments);
   
            // bind a listener for when the notification is displayed
            result.addEventListener("display", function() {
                // do something when the notification is displayed
                // use img, title, and body to read the notification
                // YOUR TRIGGERED CODE HERE!
            });
   
            return result;
        }
    })();
   

2. Next, include notifhook.js in your web_accessible_resources list in your manifest.

3. Finally, in a content script, inject a <script> element into the page with notifhook.js as its src:

    var s = document.createElement("script");
    s.src = chrome.extension.getURL("notifhook.js");
    document.documentElement.appendChild(s);
   

You might be tempted to just use notifhook.js as your content script, but that won't work because the content script and the web page have separate execution environments. Overwriting the content script's version of webkitNotifications.createNotification won't affect the Google Calendar page at all. Thus, you need to inject it via <script> tag, which will affect both the page and the content script.