Hell is other people’s JavaScript.
Third-party scripts are probably the #1 cause of poor performance and bad UX on the web.
I like the look of this proposal that would allow authors to have more control over network priorities for third-party iframes—I’ve already documented how I had to use a third-party library to fix this problem on the Salter Cane site.
Trust no one! Harry enumerates the reason why you should be self-hosting your assets (and busts some myths along the way).
There really is very little reason to leave your static assets on anyone else’s infrastructure. The perceived benefits are often a myth, and even if they weren’t, the trade-offs simply aren’t worth it. Loading assets from multiple origins is demonstrably slower.
Web development follows a familiar cycle. First we glue together a solution with whatever we have — JavaScript, image hacks, Flash, anything. Then the platform matures, and CSS or HTML eventually makes that same workaround native. Rounded corners, custom fonts, smooth scrolling, sticky positioning: all of these started as JavaScript-heavy hacks before CSS turned them into a single declaration.
We are in another one of those transition moments. A new wave of long-requested CSS features is finally landing, and many of them are explicitly designed to replace patterns that used to require JavaScript. Not as approximations — as first-class platform primitives that handle the edge cases, run in the right thread, and need zero dependencies.
Frameworks like React are often perceived as accelerators, or even as the only sensible way to do web development. There’s this notion that a more “modern” stack (read: JS-heavy, where the JS ends up running on the user’s browser) allows you to be more agile, release more often with fewer bugs, make code more maintainable, and ultimately launch better sites. In short, the claim is that this approach will offer huge improvements to developer experience, and that these DevEx benefits will trickle down to the user.
But over the years, this narrative has proven to be unrealistic, at best. In reality, for any decently sized JS-heavy project, you should expect that what you build will be slower than advertised, it will keep getting slower over time while it sees ongoing work, and it will take more effort to develop and especially to maintain than what you were led to believe, with as many bugs as any other approach.
Where it comes to performance, the important thing to note is that a JS-heavy approach (and particularly one based on React & friends) will most likely not be a good starting point; in fact, it will probably prove to be a performance minefield that you will need to keep revisiting, risking a detonation with every new commit.
Every millisecond you spend executing JavaScript is a millisecond the browser can’t spend responding to a click, updating a scroll position, or acknowledging that the user did just try to type something. When your code runs long, you’re not causing “jank” in some abstract technical sense; you’re ignoring someone who’s trying to talk to you.
This is a great way to think about client-side JavaScript!
Also:
Before your application code runs a single line, your framework has already spent some of the user’s main thread budget on initialization, hydration, and virtual DOM reconciliation.
Or, more precisely, why use React *in the browser*?
In which I find a tagline for Web Day Out and a tagline for React.
How I switched to high-resolution maps on The Session without degrading performance.
Going back to school in Amsterdam.
DOM scripting and event handling.