The promise of Rust is safe and fast low-level development. What is the primary selling point of using rust for webdev? Speed? I can mainly see disadvantages when using rust for this scenario.
- Rust compiles to WASM, not JS, so you can actually take advantage of its low-level nature in the browser for performance critical tasks within your app.
- The Rust code you're writing is still statically compiled, so you still get to take advantage of Rust's typechecking and IDE features.
- Some people just like writing Rust code more than Javascript. Part of the reason Javascript took off so quickly on the server was because there's a huge productivity boost from using one language everywhere. Similarly, if you love Rust but think that Javascript paradigms around prototypes, closures, or `this` are weird, you get to ignore that and take advantage of one of the best app distribution platforms in the world without learning a new language.
I pretty solidly hold to the position that increasing language diversity on the web is a good thing. Particularly with Rust, since they've put in the work to have proper, accessible support that's still separating app logic from DOM layout and CSS styling. I'm really happy with how their community has approached building out Rust as a first-class language on the web rather than just as native language that happens to have a web compile target.
Yeah, but the problem is that 99.9% of front-end work is only performance-critical for DOM rendering (the 0.1% is stuff like video encoding & decoding) and WASM can't help with that.
In which case, rust still isn't a good fit for a front end library (Unless you are patching in support for a new codec into old browser).
Frankly, the browser will have a faster version of the codec that can also take advantage of other hardware that you wouldn't want to expose to WASM.
There are two meanings of "DOM rendering" in the context of UI-as-a-function-of-state libraries: 1) generating the virtual DOM from data, and 2) modifying the real DOM to match it. Arguably there's even a 3) browser reflow as a result of those DOM changes.
You're right that 2 and 3 can't really be helped by WASM. But 1 can, and while it's not usually the bottleneck, it certainly can be. At my last company it was not terribly uncommon that fixing UI jank came down to eliminating unnecessary React render function calls because the sum total of them all - running the actual JavaScript logic - was taking too long. Assuming yew computes the virtual DOM in WASM (I don't see how it could be otherwise), the performance increase could definitely be beneficial for certain highly-complex apps.
When you've got 10,000+ component instances on a page, tiny bits of render logic add up. You can identify whether actual JS logic is your bottleneck (and to an extent, which JS is your bottleneck) through profiling.
The most common fix is to avoid calling render functions at all where possible. These are cases where the output of the render function will be identical to the previous output - which means React won't make any DOM changes - but where the render function will itself get called anyway. You can prevent this through better dirty-checks on props and state (shouldComponentUpdate, in React's case). Though if you're not careful, even those comparisons can become a limiting factor (not often, but sometimes). Immutable data structures like those in Immutable.js and pub/sub component updates like what MobX does can help ensure comparisons don't get expensive.
Another trick is to do expensive operations like mapping over a large array ahead of time, instead of doing it on every render. Maybe you even need to perform your array transformation in-place with a for loop, to avoid allocating-and-copying. This is especially true if you do multiple array operations in a row like filtering, slicing, reducing. Memoization of data that gets re-used across renders is a generally helpful pattern.
Another huge factor in this case is concurrency: JavaScript runs on the same browser thread as reflow and all the rest, meaning that all of this JS logic blocks even non-JS interactions like scrolling and manifests very directly as UI jank. React rendering cannot happen in a worker thread because React requires direct access to the DOM API (element instances, etc), and worker threads cannot share memory directly with the main thread; it's message-passing only (the upcoming React Concurrency project will help alleviate this problem, but doesn't directly solve it). Rust, on the other hand, can share memory between threads, meaning that in theory (assuming Yew takes advantage of this) renders can happen in parallel. Even if they don't, WASM already lives in a separate thread from the main DOM, which does mean it will probably incur some constant message-passing overhead, but it should never block reflow. And that would go a very long way towards preventing user-facing jank.
The average web app doesn't run into these problems, and usually they can be optimized around, but when you do run up against these limits any across-the-board speed improvement that raises the performance ceiling can reduce the amount of micro-optimization that's necessary, reducing the cost in developer time and likely improving readability.
Also, many of the optimizations I listed above can make code less readable in small ways. Many of them are things you should not do eagerly (premature optimization is the root of all evil), and should only go back and do once you've identified a specific problem. If an across-the-board speed increase prevents them from ever becoming problems, that's a win.
If you're thinking I'm a JS-hater, you're wrong. I think JS is a good language and I love using it where it's appropriate. But there are some usecases that benefit from a faster technology, and it's absolutely bonkers to try and argue that that technology shouldn't exist because "you can still make something slow with it if you really try".
1) We had a querying interface that would allow the user to construct a query and then it would return potentially thousands of results, asynchronously, over a websocket. We only displayed the first 300 on screen at a time, but sometimes the updates would come in so rapidly during that first 300 that one render wouldn't be finished before more results were available and the next render triggered. Things would get really backed-up and the UI would hang for multiple seconds at a time. So we decided to throttle the rendering - get the results as fast as possible, but only render once every 500ms or something. But during this time the user still might want to scroll around and look at other parts of the page, so we didn't want it to pause for 100ms every 500ms. It was a constant battle to keep things responsive while all this was going on.
2) We had another screen that would load another massive list (thousands and thousands) of entities as soon as you visited. These also came in gradually over time to spare the user from waiting for the last result before they could see the first. Similar deal: we throttled, but we needed to keep things responsive even during that throttling because the user would be scrolling up and down the results as they were coming in.
I never claimed that switching languages would have magically solved all our problems, but in our case it could've been a significant boon to performance which could've been one factor of many that contributed to a solution, and I just can't figure out why you have such a problem with that idea.
I am a data engineer now and sometimes have to build web interfaces for scrolling large data tables. Just like in the 3d graphics world, the trick to responsiveness is culling. Only download and display the amount of data that the user will see at a given time, plus some overhead so the user never sees gaps when scrolling.
While Rust may have solved the problem in #1, it is unlikely to solve the problem in #2 because you are also fighting the network where Rust is useless. Need culling.
There are some edge cases where these techniques can work - like if you have a really simple layout, and you can give a fixed-height to every item (table row or otherwise), and you assume the user is never going to resize their browser window - but it isn't nearly as obvious of a win as it is for 3D rendering and we just never decided it was worthwhile to try going down that rabbit-hole.
Exactly the same for 3d graphics. The auto-positioning is different but conceptual similar.
Yes B is my recommended approach. Since we are talking about performance, we should really be putting limits on what fast and slow mean. That is because it doesn't really matter if something is fast or slow, what matters is the performance difference between different approaches.
For B on average, performance will in the microsecond range, DOM rendering will be in the millisecond range, and the network is >100ms to seconds range. It is unlikely that B will be equal or slower to brute force rendering everything. Those X microseconds spent figuring out the culling window saves Y milliseconds rendering and saves Z milliseconds to seconds querying the network.
Most "performance" problems on the web are solved by simple techniques like virtualization, pagination, pushing expensive calculations to the server, avoiding round-trip requests, or basic UI/UX improvements. The only time I would care about JavaScript's actual runtime performance if I were doing something crazy like 3d rendering in the browser and that's a completely different set of problems than React or Yew are set up to handle.
I would use WebGL and WebGPU for that, and AssemblyScript for WebAssembly, so nothing that Rust would make a major difference.
Talking about perf without understanding the problem domain is a common mistake Rust folks tend to make.
I don't think there is enough push for people to switch to a new language just for performance sake in front-end land. JS ain't that bad, and performance is certainly achievable by careful and incremental optimization.
What a nightmare to debug!
As surprising as it might sound -- not really. There's a small-but-non-trivial amount of overhead involved in calls between WASM code and the DOM API's, plus (de)serialization.
It's more of a familiarity/existing tooling thing. Same as Blazor in C# writing web apps in that. If your entire team only knows C# and you have all your existing tooling there then it could seem an appealing option.
But there's also the argument for more stringent safety with Rust compared to IE, Typescript.
My understanding is that this is going to get a lot better in the future though -- last I checked the plan was for WASM to eventually have direct bindings to DOM APIs, at which point you won't need to interact with JS at all.
https://github.com/WebAssembly/interface-types/blob/master/p...
I wouldn't think it's far behind. The Multi-Value proposal, which had huge ramifications, was recently accepted in April so WASM is clipping along at a fair pace still.
I've done a fair bit of benchmarking/performance experimentation with compiling Rust/Go/Zig etc to WASM (including with SIMD or parallelization enabled).
It'll be really interesting watching the progress of V8 + WASM SIMD proposal, it's been enabled behind a flag in V8 for some time now.
> often running faster than WASM
This seems pretty counter to everything I've read about WASM - V8 is some black magic, but WASM should run far faster. What language was the WASM blob compiled from? Mozilla has also demonstrated that they can send the DOM to a WASM blob, have it perform the necessary transformations and return it, faster than JS could perform the same transformations itself.
Now I'm somewhat tempted to write a js implementation to actually compare.
I'm going to be looking into the other way around: writing a web app in it to learn it. Seems like a great use case that would make it easier for me to learn, as someone who has experience with web apps and not so much with desktop software.
Rust started on the back-end but is fairly likely to spread to the front-end in the future for the same reason. One of the advantages will again be that folks who are experts in Rust will be able to use their language of choice for front-end work too.
Beyond this, I would argue that Rust's type system is a significant draw for many folks as well. I dare say it has a lot more potential than Elm, a Haskell-like language designed just for web development.
So if you're already using Rust for the app backend, I think the interest is more about using the same language in the back and in the front. Since nowadays one usually wants a typed Javascript (e.g. Typescript) anyway, it is far shorter of a leap to Rust.
I don't know why it seems React apps are some of the worst offenders, but I think it has to do with hooks injecting context components everywhere (at least that's what it looked like last time I popped open React dev tools). I'm guessing that out of tree state tracking is particularly memory intensive.
Web assembly will see a whole new round of people trying to do monoglot programming. Which I welcome, because I like JavaScript well enough but I don’t like writing it all day, every day, for years at a time.
I agree it's a bit too far out for a lot of javascript/typescript developers. But then the Rust community has a lot of former full stack refugees joining it. My observation is that "full stack development" using javascript is a phase developers go through before upgrading to some other language. You see similar patterns in the Go community. Both communities have lots of people who used to do lots of web and node.js development.
My money is more on languages like Kotlin, C#, and Swift crossing over to the browser. Both already have wasm compilers that are still need a lot of work. This work only kicked off for Kotlin fairly recently. Kotlin also has a decent javascript transpiler that you can use right now. Both Swift and Kotlin are very popular for mobile UI development. C# has been used extensieley for Desktop and web server development. Obviously these languages come with lots of features that make them very suitable and popular for exactly the kind of stuff people use Javascript (and Typescript) for.
I haven't done much with Swift and C# but Kotlin is great for this. Most of my experience with that language is server side but I have done a few things with kotlin-js as well as some Android stuff. As of a few months ago, the kotlin-js tooling is getting to the point where it's a very solid choice. It builds, it eliminated dead code, it runs webpack for you, etc. The upcoming version (1.4.0) is currently available as a release candidate and includes something called Dukat. Dukat generates kotlin type headers from typescript type headers for npm dependencies. So that means you can integrate a lot of existing npms if you have to. Also the build tools integrate with webpack and you can target both the node.js ecosystem and the browser ecosystem.
Most of the bottlnecks for adopting either transpilers or wasm compilers in this space is the relative immaturity (or lack off) mature alternatives to popular javascript frameworks. You can do react apps in a bunch of languages now but it just feels wrong to do it. The pattern you see in other language communities is that they pretty much start rolling their own alternative frameworks. In any case, the amount of third party code making it to a browser is typically not that much for most webapps. For all it's popularity, the react run-time code is not that large. A few hundred KB is considered a lot.
As far as I know, Rust's WASM performance is much more uniform than JS'.
Of course, maybe just because it uses WASM it doesn't automatically have to be faster - but this looks promising.