Responsible JavaScript

A presentation at Prairie Dev Con in in Winnipeg, MB, Canada by Jeremy Wagner

While the performance of JavaScript engines in the browser have seen continued improvement, the amount of JavaScript we serve increases unabated. We need to use JavaScript more responsibly, which—in part—means we must rely on native browser features where prudent, and know when too much JavaScript is just that: Too much.

In this talk, we’ll explore what happens to performance and accessibility when devices are inundated with more JavaScript than they can handle. We’ll also dive into some novel techniques you can use to tailor delivery of scripts with respect to a user’s device capabilities and network conditions. When you walk out of this session, you’ll be equipped with new knowledge to make your sites as fast as they are beautiful.


The following resources were mentioned during the presentation or are useful additional information.

  • Responsible JavaScript: Part I

    The web is drowning in a sea of JavaScript, awash with unnecessary bloat, inaccessible cruft, and unsustainable patterns. Jeremy Wagner plots a course to navigate the JavaScript Sea responsibly by building the right things the right way and using the web platform the way it was meant to be used.

  • Bundlephobia

  • HTTP Archive

  • WebPageTest

  • Paint the Picture, Not the Frame: How Browsers Provide Everything Users Need

    Designers want to create fully branded experiences, which often results in customized highlighting colors or pixel-perfect typography. While these design touches can enhance the experience for some, they can render the experience inaccessible for others. Designer Eric Bailey makes a case for leaving key accessibility features to the browser to ensure the most accessible experience possible.

  • quicklink

    Faster subsequent page-loads by prefetching in-viewport links during idle time.

  • dnstradamus

    A prognosticating script that prefetches DNS information for outbound links.

  • Hybrid Lazy Loading: A Progressive Migration To Native Lazy Loading

    Native lazy loading is coming to the web. Since it doesn’t depend on JavaScript, it will revolutionize the way we lazy load content today, making it easier for developers to lazy load images and iframes. But it’s not a feature we can polyfill, and it will take some time before it becomes usable across all browsers. In this article, you’ll learn how it works and how you can progressively replace your JavaScript-driven lazy loading with its native alternative, thanks to hybrid lazy loading.

  • Babel 6: Loose Mode

    Babel’s loose mode transpiles ES6 code to ES5 code that is less faithful to ES6 semantics. This blog post explains how that works and what the pros and cons are (spoiler: normally not recommended).

  • Third-party Web

  • How we shaved 1.7 seconds off by self-hosting Optimizely

    We recently deployed a change to that loaded a piece of 3rd party JavaScript from our own server instead of the vendor’s server. This change shaved 1.7 seconds off of the start render time.

  • The Unacceptable Persistence of the Digital Divide

    Millions of Americans lack broadband access and computer skills. Can President Trump bring them into the digital economy?

  • Take a (Client) Hint!

  • Adapting to Users with Client Hints

    Developing sites that are fast everywhere can be a tricky prospect. The plethora of device capabilities—and the quality of the networks they connect to—can make it seem like an insurmountable task. While we can take advantage of browser features to improve loading performance, how do we know what the user’s device is capable of, or the quality of their network connection? The solution is client hints!