Virtual DOM in Elm • Hacker News Board

Re: Virtual DOM in Elm

#21

Post by mudetroit » Mon, Jul 21, 2014, 4:22 PM UTC

syntern wrote: post #9

pestaa wrote: post #8

Earlier quoted context omitted.

I've seen some AngularJS vs React benchmarks a while back. I believe it was http://jsperf.com/angular-vs-react/5 I consistently got the result of Angular utterly and completely destroying React. Initially I blamed the virtual DOM approach, but after seeing other frameworks utilizing it and outperforming Angular by a huge margin, it seems to me that React is not written for performing well on small DOM documents. (The…

Our performance benchmarks suggest that application performance is most certainly better off with: (a) DOM reuse (b) calculating expensive things only once (c) reducing GC pressure == not discarding/recreating things (d) coordinating actions that may trigger reflow. It is independent of what framework you are using. My limited understanding of React is that it fails in (a), (b) and (c), and only limited measures can…

React can handle all of your items just fine depending upon usage.

(a) Using the key property, will give React a manner to determine likeness of elements

(b) Don't calculate the expensive things at render time, do them when loading or modifying state.

(c) Is related to a, but I haven't run into large problems with this personally.

(d) React does batch changes to an extent I believe.

Re: Virtual DOM in Elm

#22

Post by andrewljohnson » Mon, Jul 21, 2014, 4:23 PM UTC

All of the empty brackets to describe the virtual DOM looks bad to me. I'm curious if this is regarded as a language smell.

Re: Virtual DOM in Elm

#23

Post by underwater » Mon, Jul 21, 2014, 4:25 PM UTC

syntern wrote: post #9

pestaa wrote: post #8

Earlier quoted context omitted.

I've seen some AngularJS vs React benchmarks a while back. I believe it was http://jsperf.com/angular-vs-react/5 I consistently got the result of Angular utterly and completely destroying React. Initially I blamed the virtual DOM approach, but after seeing other frameworks utilizing it and outperforming Angular by a huge margin, it seems to me that React is not written for performing well on small DOM documents. (The…

Our performance benchmarks suggest that application performance is most certainly better off with: (a) DOM reuse (b) calculating expensive things only once (c) reducing GC pressure == not discarding/recreating things (d) coordinating actions that may trigger reflow. It is independent of what framework you are using. My limited understanding of React is that it fails in (a), (b) and (c), and only limited measures can…

None of the things you have guessed about React are true.

Re: Virtual DOM in Elm

#24

Post by masklinn » Mon, Jul 21, 2014, 4:26 PM UTC

colinramsay wrote: post #7

My first thought when looking at the benchmarks is that I find it strange that Backbone is faster than React. Not that I imagine Backbone to be slow, particularly, just that this article is about one of React's key features - the virtual DOM - and that's something which Backbone doesn't have. I'd expect to see React up there with Om, Mercury & Elm. I've just had a look at the code and React is using a localstorage ba…

> I'd expect to see React up there with Om, Mercury & Elm.

Not by default because it's missing laziness and immutability: because just about everything in javascript is mutable, React can't prune out the changeset as the developers could be modifying the application state behind its back in ways unknown (or worse, could be using state which is not under React's control, neither props nor state, but globals and stuff).

That is, for safety/correctness reasons the default `shouldComponentUpdate` is `function () { return true; }`. The result is React has to re-render the whole virtual DOM tree (by default) and the only possible gain is when diffing the real and virtual trees.

Because Clojurescript and Elm are based on immutable structures they can take the opposite default (and if you're going behind their back and mutating stuff it's your problem).

Also, I'm not sure React defers rendering until animationFrame.

An optimized React application (or at least one which uses PureRenderMixin[0]) ought have closer performances to the others's (Om is a bunch of abstractions over React after all, so you should be able to have at least as good performances in pure React as you get in Om).

[0] http://facebook.github.io/react/docs/pure-render-mixin.html

Re: Virtual DOM in Elm

#25

Post by sisk » Mon, Jul 21, 2014, 4:28 PM UTC

syntern wrote: post #9

pestaa wrote: post #8

Earlier quoted context omitted.

I've seen some AngularJS vs React benchmarks a while back. I believe it was http://jsperf.com/angular-vs-react/5 I consistently got the result of Angular utterly and completely destroying React. Initially I blamed the virtual DOM approach, but after seeing other frameworks utilizing it and outperforming Angular by a huge margin, it seems to me that React is not written for performing well on small DOM documents. (The…

Our performance benchmarks suggest that application performance is most certainly better off with: (a) DOM reuse (b) calculating expensive things only once (c) reducing GC pressure == not discarding/recreating things (d) coordinating actions that may trigger reflow. It is independent of what framework you are using. My limited understanding of React is that it fails in (a), (b) and (c), and only limited measures can…

All of those points are precisely what React addresses.

The virtual DOM determines which mutations are necessary and performs only those, batched. It also reuses DOM nodes as appropriate. DOM nodes can even be keyed against data in the case that, between transitions, it isn't entirely clear which nodes correspond to which data.

Re: Virtual DOM in Elm

#26

Post by takeoutweight » Mon, Jul 21, 2014, 4:30 PM UTC

LukeHoersten wrote: post #11

Anyone know of a Haskell or proper Haskell subset that can do something similar (hopefully batteries included)?

Absolutely not "batteries included" but I've put some work into a React interface for Haste, which is a Haskell->JS compiler.

https://github.com/takeoutweight/shade

Re: Virtual DOM in Elm

#27

Post by jlongster » Mon, Jul 21, 2014, 4:30 PM UTC

smizell wrote: post #19

jlongster wrote: post #14

Earlier quoted context omitted.

Not yet, I've been dying to dig into this for months but now just getting some time to do so. I'm rewriting my blog with lots of cool technologies like this and going to open-source it and write up about it. http://jlongster.com/

Cool, I'll keep an eye out. Any reason to use React+Mori over Om other than more familiarity with JavaScript??

There is a huge amount of JavaScript developers that can't jump to ClojureScript. I love CLJS, but I have a heart for the amount of JS projects out there that can't take advantage of these techniques. It's really important that we borrow from good research and make it available to JS so that existing projects can begin integrating them, because most of them will not jump to a completely different language.

Re: Virtual DOM in Elm

#28

Post by vjeux » Mon, Jul 21, 2014, 4:30 PM UTC

syntern wrote: post #9

pestaa wrote: post #8

Earlier quoted context omitted.

I've seen some AngularJS vs React benchmarks a while back. I believe it was http://jsperf.com/angular-vs-react/5 I consistently got the result of Angular utterly and completely destroying React. Initially I blamed the virtual DOM approach, but after seeing other frameworks utilizing it and outperforming Angular by a huge margin, it seems to me that React is not written for performing well on small DOM documents. (The…

Our performance benchmarks suggest that application performance is most certainly better off with: (a) DOM reuse (b) calculating expensive things only once (c) reducing GC pressure == not discarding/recreating things (d) coordinating actions that may trigger reflow. It is independent of what framework you are using. My limited understanding of React is that it fails in (a), (b) and (c), and only limited measures can…

(a) You can use the key attribute in order to get DOM reuse. If you are looping over N keys then React is going to reuse the nodes and move them around.

(b) You can implement shouldComponentUpdate in order to have a quick way not to re-render a sub-tree if nothing changed.

(c) See (b) but we're also working on changing the internal representation of the virtual DOM to plain js objects that can be reused[1]. We were super worried about GC but it turns out that it hasn't been the bottleneck yet for our use cases.

(d) If you are writing pure React, all the actions are batched and actually, it's write-only, React almost never reads from the DOM. If you really need to read, you can do it in componentWillUpdate and write in componentDidUpdate. This will coordinate all the reads and write properly.

A really important part of React is that by default this is reasonably fast, but most importantly, when you have bottlenecks, you can improve performance without having to do drastic architecture changes.

(1) You can implement shouldComponentUpdate at specific points and get huge speedup. We've released a perf tool that tells you where are the most impactful places to[2]. If you are bold, you can go the route of using immutable data structures all over the place like Om/the elm example and you're not going to have to worry about it.

(2) At any point in time, you can skip React and go back to raw DOM operations for performance critical components. This is what Atom is doing and the rest of their UI is pure React.

[1] https://github.com/reactjs/react-future/blob/master/01%20-%2... [2] http://facebook.github.io/react/docs/perf.html#perf.printwas...

Re: Virtual DOM in Elm

#29

Post by nickthemagicman » Mon, Jul 21, 2014, 4:38 PM UTC

Anybody have any good reviews on elm?

Re: Virtual DOM in Elm

#30

Post by matchu » Mon, Jul 21, 2014, 4:44 PM UTC

asolove wrote: post #18

colinramsay wrote: post #7

My first thought when looking at the benchmarks is that I find it strange that Backbone is faster than React. Not that I imagine Backbone to be slow, particularly, just that this article is about one of React's key features - the virtual DOM - and that's something which Backbone doesn't have. I'd expect to see React up there with Om, Mercury & Elm. I've just had a look at the code and React is using a localstorage ba…

(Edit: posted this comment before I read the article, doh.) These is certainly something wrong with the benchmark. Since Om is a layer on top of React, it is obvious that React itself cannot be necessarily slower than Om. (Perhaps idiomatic React usage is slower than idiomatic Om usage for this case, though?)

See the article's discussion of immutability in Elm. Om has the same immutability property, so configures React to take advantage of that property, skipping vanilla React's property diffing.

edit: Rather, see masklinn's comment that describes what actually happens. Point being, vanilla React does extra work to account for anything a developer might do, but allows Elm and Om, which have more rigorous standards for their users, to override that behavior.