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Comment by Bolkan | Hacker News Reader

JS works in mysterious ways.

I think that is the point, is that it does not. It is code, and it does what it is told. But it is quite possible to be a professional dev without fully understanding exactly how and why your frameworks doing their thing, so it feels hand-wavy and mysterious.

I'm among the React developers who don't really know how it works under the hood. Recently I needed to code a UI that required mouse drag events. It ran like a pig when I did it in React.

I tried a few things to speed it up, but eventually gave up and did the UI in plain old Javascript. It runs a hell of a lot better, but the code does feel a lot more flimsy.

Edit: Here's a demo of the UI I built https://www.youtube.com/watch?v=Wt71bNYe3qc

I'm no expert, but mouse drag events in React are fairly simple to get working performantly, even without understanding how it works under the hood. There are even many libraries that provide functionality, all without it running 'like a pig'.

Also:

> Can pigs run fast? Domestic pigs can run as fast as 17 km/h while wild pigs can reach a speed of 30 km/h!

Yes, but I didn't want to use a library because I was doing something a bit out of the usual case.

I do like understanding my code as much as possible. So I was choosing between: 1. Understand React better, and reading about the "React" way to use these mouse events. 2. Doing it in VanillaJS

>I do like understanding my code as much as possible. So I was choosing between: 1. Understand React better, and reading about the "React" way to use these mouse events. 2. Doing it in VanillaJS

The great thing about the "React" way of doing things is that it's just the JavaScript way of doing things.

React can be summed up entirely as: "a function that takes in props and returns rendered HTML". It is not a framework. There is no black magic. There are no idioms. There are no batteries included.

Anything else you do with it beyond that is entirely up to you.

That’s a bit too strong imo. There is magic, and it can generally be found in implicit re-render conditions.

"Rules of hooks" is a thing.

My point was not to use a library, but that many others have implemented functionality in libraries without performance decreases. Granted, your use case may be special to the point where vanilla JS is better, but given how many libraries are out there, as well as how many may simply be poorly implemented yet still work fast, makes me wonder what you were indeed doing.

There is nothing about react that requires you to understand "how it works under the hood" to use mouse events in react. You just need to sit down and read the tutorials and learn to use react properly. Try the new beta docs.

True, but I'm quite happy using VanillaJS. I'd like to avoid React as much as possible in the future.

It's not unlikely that you missed some hints of the latter part of the article (JS equality for functions or objects) although it's difficult to say without seeing the code.

Draggable UI (w/o libraries) is one of the places I enjoy React most, maybe re-rendering wasn't to blame. Might have been an issue under the hood (as drag fires multiple times a second)? From the article:

> I think as developers, we tend to overestimate how expensive re-renders are. In the case of our [pure] component, re-renders are lightning quick.

> If a component has a bunch of props and not a lot of descendants, it can actually be slower to check if any of the props have changed compared to re-rendering the component.

You seem to be conflating javascript and react here, and even if you weren't, the entire point of this article is that nothing works in mysterious ways.

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