Ironically, many modern SPAs are significantly slower than the traditional apps they replaced. Try using Twitter's webapp on a non-premium phone, for example.
Sometimes it's regrettable that the webdev truck has no rear-view mirror.
Rerendering and recomputing too much (ever encountered these chains of map() and filter() in render()?), many API calls, huge icon sets, huge custom fonts, CSS frameworks and JS frameworks, huge dependency trees with many instance of the same lib running sometime in several versions, big bundles... This heaviness in the name of convenience and branding is not free, it forces people to ditch perfectly fine hardware, which has a high environmental cost... not directly paid by people funding the code).
One of my pet peeves is managed text inputs, where render() is called each time you type a character, for a whole component tree if you are not careful and you happen to pass the content to some parent for some reason. Typing a message in Mattermost on the PinePhone is painful for this reason, there's just no reason typing should be slow even on slow hardware but managed component is considered good practice.
Making people buy newer / powerful and making people wait and using too much energy should be considered bad practice.
I attempted to build a startup product using a vanilla JS SPA when I was a founding engineer, and the result was predictable: it worked great for me, but nobody I hired wanted to learn some random guy's vanilla JS codebase. I've since resigned myself to using React simply because that's what developers expect, despite all the headaches.
For what it's worth, we ended up migrating to Mithril in the V2 of that startup's product. We all enjoyed Mithril and it scaled really well for us, but my team did have some apprehension about their React skills falling behind.
This hits the nail in the head.
A single high-res background image weights more than all the code in a complex webapp. If that image is required to pull the first contentful paint then the page will feel slow.
It matters nothing if your JavaScript is just a hello world console log. That background image is in the critical path.
Bullshit. All you need to track a user is data you send as part of a HTTP request. Pushing metrics is a fire-and-forget HTTP request away.
The internet feels slower because we're using way more of it, not only in the increased complexity of webapps to improve user experience and implement features but also in the volume of data we're transferring around.
> running A/B tests
A/B tests just means settings/feature flags and metrics. Feature flags is used in way more things than behavioral studies.
> include recording user sessions
User sessions are recorded since ever with zero performance penalty. The very same HackerNews page you're now browsing is tracking your user session whenever you login. That's not it.
> Back "before SPAs" we just weren't doing as much crap in the browser.
Right, and life sucked back then. Why do you think Flash was so popular?
It's trendy to shit on the status quo but it also is low-effort and lacks any insightfulness.
Browsers impose a limit on concurrent requests (usually 6 per hostname) for a reason - HTTP requests, be they too many or too large, are one of the largest performance problems in a typical site. Just because it's easy to fire-and-forget an HTTP request doesn't mean it doesn't have a performance impact, especially in apps that are already network-chatty. I think you know this because you go on to list "the volume of data we're transferring" as a performance bottleneck, and obviously that's done through HTTP requests. Also, in the real world analytics installations virtually always include installing a third party library i.e. google analytics, so you're taking hits to download the library, interpret the source, run the code alongside your app, usually in the same thread, all before you've fired any of those HTTP requests.
> A/B tests just means settings/feature flags and metrics
I'm aware of the definition. If you are implying that conditionally loading settings or feature flags and tracking associated metrics doesn't have a performance impact, I would disagree. It is usually possible to implement a given A/B test with minimal performance impact, but in practice these are absolutely a contributor to the kind of bloat I'm frustrated with.
> sessions are recorded since ever with zero performance penalty
It sounds like you're talking about logs. I'm talking about "session replay" features provided by companies like FullStory and Sentry that allow you to replay every mouse move and keystroke of your users.
> It's trendy to shit on the status quo but it also is low-effort and lacks any insightfulness.
By this point in your comment I think you forgot what we were talking about. I was arguing that the architecture of modern SPAs shouldn't bear the blame for bad performance; my point being that whether or not we continued to use server-generated HTML we would still be suffering from similar problems of bloat today. The "status quo" that I'm shitting on is taking lazy approach to performance management and injecting way too much cruft; unless you work for an analytics provider I'm not sure why you would be opposed to that stance.
All software becoming slower is a already a meme. This isn't exactly a SPA issue.
> Sometimes it's regrettable that the webdev truck has no rear-view mirror.
The "software is getting slower" meme was the Hallmark of Java in the server when it was released in the 90s. This is nothing new, or specific to web dev.
Also, I feel you're grossly misrepresenting the problem. Reddit's mobile page is considerably slower than the old reddit page, but it's perceived performance is quite good. All posts are cached and instead of full page reloads it just switches content virtually instantly.
It might be fancy to shit on everyone else's work, but this only happens if you lack objectiveness and sincerity.