It's also very easy to mess up the performance due to architecture when using modern frameworks. For example: as much as SPAs are reviled, if you have a complex enough web application with heavy components, having it being an SPA might be better in terms of perceived speed than having it do a full reload on every navigation.

This is a mistake that I see far too many government and utility sites making.

Except that in React writing clean code will actually make your application faster.

Re-renders are incredibly cheap in the big picture. They are not a source of performance bottlenecks in 99% of real world applications

So why do 99% of real world applications run like garbage? What’s the culprit?

> So why do 99% of real world applications run like garbage?

If you're really interested in the impact of performance issues on everyday life, you need to provide concrete examples instead of putting up unverifiable strawmen.

The truth of the matter is that 99% of real world applications run just fine, and it doesn't pay off to invest in shaving milliseconds here or there. Would it be desirable to have a magic wand to improve some edge cases? Yeah, why not? Is it worth to pay people to spend time with a stopwatch at hand to shave off these milliseconds? Not really. It's all about tradeoffs, and there is no real world payoff in wasting developers' time to shave off that millisecond here or there.

The promise of frameworks like React is that you write code in their way and they take care of performance, because functional, declarative and all that. You just use primitives and don’t control how it all works under the hood. Coping may be a good strategy here, but isn’t a good argument.

You basically waste millions of seconds of users' lifetime instead :)

Not to mention that web apps redrawing everything whenever they feel like it can almost give motion sickness, lead to clicks on the wrong things etc.

Yeah, but users' time is worthless.

You know, I started on some concrete examples for you, but I had to stop and back up. Really? You can't think of any examples yourself? The modern web is absolute hell to use if you aren't on modern hardware. Try it sometime; use a 10 year old phone, or an old computer that wasn't built top-of-the-line.

There's so much hardware out there that can run native applications just fine, that can play back HD video, that can run complex 3D real time video games, but crawl like molasses when loading your average webpage. Facebook and YouTube are terrible offenders, but so are your average blogs. Many banking websites are terrible (yet they don't have to be; my local credit union has a zippy website that looks attractive to boot, has modern design elements, etc.).

Maybe the hardware you're running is eye-wateringly fast, or maybe it's just barely fast enough and you don't need the cycles for anything else. But we're not talking milliseconds. We're talking order(s) of magnitude. I can't bring myself to believe you don't see at least some of it, if you just open your eyes and look around.

> Really? You can't think of any examples yourself?

"Unverifiable!", he wrote from within a web browser.

Since we're talking about React, Facebook's web app is incredibly slow to me, and typing text in some fields is slower than me. As in, it sometimes takes a second for the letters to start showing. And no, it's not a browser rendering issue (even if it were it would be terrible), as disabling JS in Safari brings back the performance.

Another app that I'm not sure if it's React or not is New Reddit. It is significantly slower on my computer and on a lot of people's computer and sometimes you have to refresh the page because it consumes too much memory.

I can come up with other local examples, from Germany. Vatenfall's website seems to "traditional" page navigation, but the content is loaded via a framework. Due to having to reinitialize everything, text takes up to 5 seconds to appear when using the back button or when navigating for page to page. Similar things happen in the German Agentür fur Arbeit.

My hot take is that React doesn't directly _cause_ slow performance, but that React is so well marketed as a first place to start for new programmers that the bar for quality is much lower than other industries (like game programming, or even "vanilla JS" which is increasingly seen as an advanced approach).

The trouble with this attitude, is that it misses the fact that the _range_ of computing power of devices which ordinary people use is probably greater now than it's ever been.

Let's not even get into low end phones in developing countries or bargain basement android tablets, let's stick with something straightforward - an ordinary PC.

I took a quick look online, sorting by cheapest first I found something with an AMD 3015e in. Based on cpubenchmark.net that gets a benchmark of 2691. Taking a look at the big list of CPUs I see that's equivalent to a powerful desktop CPU from 2008, or a decent laptop from 2012. (The Apple M2 in the current Macbook Air gets a score of 15369, just for comparison.)

So, if you're writing PC software or making a fancy web app and you want everyone to have a good experience with it then you should see how it runs on a terrible new laptop, or a 12 year old good laptop, or a 15 year old powerful desktop.

(And yeah we all have SSDs now which is much better than in the old days, and JS is generally single thread, and single threaded CPU performance has not improved so much - but I think my point still stands.)

> The truth of the matter is that 99% of real world applications run just fine, and it doesn't pay off to invest in shaving milliseconds here or there.

You're taking deep quaffs of the Kool-Aid and so are most of the people commenting on this story. General software responsiveness and reliability (i.e., usefulness) has been in decline for decades. This is an objective fact.

Writing objective reality off as mere "milliseconds", "edge-cases", or only relevant for "toy problems" exemplifies the arrogance and severe incompetence of most programmers. People are seriously trying to talk down to Casey Muratori when in all likelihood they haven't accomplished even 1% as much as him as programmers.

I get it—no one wants to leave fantasy-land as long as the easy money is flowing. But sooner or later the glittering carriage turns back into a pumpkin.

Go to a slow website on Chrome. Open dev tools and turn on "enable paint flashing", you'll see a seizure inducing light show of re-rendering...

It's certainly a huge problem for real world applications