this post was submitted on 11 Jun 2025
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Also the difference between TS and JS doesn't make sense at first glance. ๐คทโโ๏ธ I guess I need to read the research.
My first thought is perhaps the TS is not targeting ESNext so they're getting hit with polyfills or something
It does, the "compiler" adds a bunch of extra garbage for extra safety that really does have an impact.
I thought the idea of TS is that it strongly types everything so that the JS interpreter doesn't waste all of its time trying to figure out the best way to store a variable in RAM.
TS is compiled to JS, so the JS interpreter isn't privy to the type information. TS is basically a robust static analysis tool
The code is ultimately ran in a JS interpreter. AFAIK TS transpiles into JS, there's no TS specific interpreter. But such a huge difference is unexpected to me.
Its really not, have you noticed how an enum is transpiled? you end up with a function... a lot of other things follow the same pattern.
Nope, have not noticed because I hate JavaScript with a passion. Thanks for educating me.
Just FYI the example that person gave would absolutely not explain a huge performance difference. I don't think they understand what they're looking at.
fair enough :D but it does happen and there are reasons for that: https://stackoverflow.com/questions/47363996/why-does-an-enum-transpile-into-a-function
Thanks! I hate JavaScript even more now ๐
No they don't. Enums are actually unique in being the only Typescript feature that requires code gen, and they consider that to have been a mistake.
In any case that's not the cause of the difference here.
This isn't true, there are other features that "emit code", that includes: namespaces, decorators and some cases even async / await (when targeting ES5 or ES6).
Ah yeah I forgot about namespaces. I don't think they're a popular feature.
The other two only generate code for backwards compatibility. When targeting the latest JavaScript versions they don't generate anything.
Ok decorators are technically still only a proposal so they're slightly jumping the gun there, but the point remains.
Only if you choose a lower language level as the target. Given these results I suspect the researchers had it output JS for something like ES5, meaning a bunch of polyfills for old browsers that they didn't include in the JS-native implementation..
Not really, because this stuff also happens: https://stackoverflow.com/questions/20278095/enums-in-typescript-what-is-the-javascript-code-doing a function call always has an inpact.
Yeah sure, you found the one notorious TypeScript feature that actually emits code, but a) this feature is recommended against and not used much to my knowledge and, more importantly, b) you cannot tell me that you genuinely believe the use of TypeScript enums โ which generate extra function calls for a very limited number of operations โ will 5x the energy consumption of the entire program.
This isn't true, there are other features that "emit code", that includes: namespaces, decorators and some cases even async / await (when targeting ES5 or ES6).
Care to elaborate?
Here's a good example: https://stackoverflow.com/questions/47363996/why-does-an-enum-transpile-into-a-function
That is not a good example. That is an immediate function call happening once when the program starts and certainly does not have a large impact like you are suggesting.