Chrome extension, jQuery, unofficial YouTube APIs
This is a YouTube feature I’ve been wanting for a while: I know there are videos, especially music videos, that I return to over and over again, and I would like to see which ones I’ve viewed the most. YouTube has a watch history but doesn’t offer a tally.
So I wanted to bolt on that feature. The YouTube Data API unfortunately does not grant access to the watch history – it was removed from the API at some point, maybe because that information is way more sensitive to privacy issues than anything else in the API? My best bet was creating a Chrome extension then which suited me well enough. I wanted to learn more about extensions anyway.
Chrome extensions are based on the time-tested combination of HTML, CSS & JS, with some specific JS APIs thrown in. I appreciated how this lowered the barrier of entry for somebody familiar with web development. The programming model is awkward though for the same reason that it is for many of these types of plugin/extension frameworks. There isn’t a real development environment – an IDE, so to speak. Notice, for example, how the developer documentation is silent on the topic of automated testing. It’s easy enough to load an extension locally in Chrome but then development becomes a tedious cycle of code editing, reloading the extension and manual testing.
My main challenge was YouTube itself anyway. Chrome extensions let you run your JS in the context of an existing page – such as the YouTube watch history page – which gives you access to the DOM, safe XHR requests to the page’s origin, and even global JS variables (not a documented feature – but the hacks work). Originally I thought I was going to scan the history via the DOM but I had to give up on that. The DOM is dauntingly complex, using a ton of web components, and scrolling down far enough to capture a sizable chunk of the history brought even my high-end MacBook to a crawl. So instead I reverse engineered the XHR requests that the page makes to browse through the history.
I decided to use jQuery because I couldn’t stomach writing raw JS. With more time and patience I would have tried setting up a more sophisticated environment with package management and something like webpack. Rest assured I would never use jQuery in a project not explicitly designated as a hack!
jQuery spaghetti notwithstanding, the result seemingly works quite well. Of course it depends on undocumented YouTube APIs and UI elements, so it will be correspondingly brittle. I released the source code on GitHub in the (probably futile) hope that, if the extension does need maintenance to keep it compatible as YouTube makes changes, somebody might be able to contribute to it.