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Node.js is able to execute TypeScript files without additional configuration

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Re: Node.js is able to execute TypeScript files without additional configuration

#21

Post by bitterblotter »

mattlondon wrote: post #8
tempodox wrote: post #2

It looks like this works by stripping away the type information, so at best it saves you a transpilation pass and doesn't improve safety.

Yeah agreed - saying "node can execute typescript files" is a bit misleading. More accurate would be "node can find-and-replace type information with spaces from .ts files and try and executing them as if they were plain JavaScript" I suspect this would only handle the most rudimentary and basic typescript files. Once you start using the type system more extensively I suspect this will blow-up in your face. It's kind…

Just to give context here, NodeJS doesnt support enums, namespaces and class parameter properties. All of these have been described as regrets by Anders Hejsberg, and none of them prevent advanced use of the type system at all.

Source: 49m 43s https://m.youtube.com/watch?v=NrEW7F2WCNA

Re: Node.js is able to execute TypeScript files without additional configuration

#24

Post by ireadmevs »

ninetyninenine wrote: post #6

Is there any movement in the node world for the runtime to be able to ascertain types? Obviously nodejs doesn't do this, but does Bun or Deno or are there plans for any of this in the future?

I believe it would be too hard to keep up with pace of TypeScript development. We should probably at some point formally define the system and allow for alternative implementations outside of the control of Microsoft.

Re: Node.js is able to execute TypeScript files without additional configuration

#25

Post by nosianu »

ninetyninenine wrote: post #6

Is there any movement in the node world for the runtime to be able to ascertain types? Obviously nodejs doesn't do this, but does Bun or Deno or are there plans for any of this in the future?

This has nothing to do with the "node world". Such an enormous feature would have to go into ECMAScript. Which is very, very unlikely to ever happen, they may as well design a new language. All those runtimes implement that spec. Expecting them to write an extremely complex new feature that is easily more complicated than everything already implemented (especially with backwards compatibility, and given that the language was not designed for this) would be a bit much.

TypeScript is for compile time checking of a language that was not designed to have them. Runtime types have very different requirements! It has to be in the language from the early design phase, otherwise it will just be a hack with many conditions, restrictions and holes.

TS Types are only partially a description of the underlying types in the code, a very big part instead is that it provides guard rails that prevent you from using a lot of perfectly fine and valid JS code that would however be incompatible with type guarantees. You pay the price of using only a part of the large space of JS code possibilities for guarantees. If you were to put that into the runtime you would end up with two different versions of the language. If you still want to support the full JS you would end with two runtimes in one (or one that has so many branches and conditions that maintaining that runtime is a real beast).

Re: Node.js is able to execute TypeScript files without additional configuration

#26

Post by pavlov »

mattlondon wrote: post #10
sisve wrote: post #4

Impressed with what Node is doing the last years, deno and bun has really made Node focus and improve. It was stuck for a while

What are the recent improvements in node itself? Last actually note-worthy improvement I heard of was properly supporting import/export (although do you still need to use the .mjs hack?), but I've been out of the loop here for sometime so would be nice to know what they've added since.

Here’s a nice overview:

https://kashw1n.com/blog/nodejs-2025/

It doesn’t cover everything, but as an old-school Node user I found several interesting features I didn’t know about.

Re: Node.js is able to execute TypeScript files without additional configuration

#27

Post by moi2388 »

mattlondon wrote: post #10
sisve wrote: post #4

Impressed with what Node is doing the last years, deno and bun has really made Node focus and improve. It was stuck for a while

What are the recent improvements in node itself? Last actually note-worthy improvement I heard of was properly supporting import/export (although do you still need to use the .mjs hack?), but I've been out of the loop here for sometime so would be nice to know what they've added since.

Do you mean.. node-worthy?

Re: Node.js is able to execute TypeScript files without additional configuration

#28

Post by dust42 »

lbltavares wrote: post #13
tempodox wrote: post #2

It looks like this works by stripping away the type information, so at best it saves you a transpilation pass and doesn't improve safety.

Yes, it can't parse enums, for example.

It is available behind an experimental flag: --experimental-transform-types

Re: Node.js is able to execute TypeScript files without additional configuration

#29

Post by 9rx »

nine_k wrote: post #20
tempodox wrote: post #2

It looks like this works by stripping away the type information, so at best it saves you a transpilation pass and doesn't improve safety.

One of Typescript's design goals is that removing all type-related parts of the source text should yield a valid JavaScript file. A typescript compiler does not generate code (unlike, say, PureScript). You can run a typechecker (such as tsc) that check various properties of your code statically, relying on the type information. It is then erased. The same applies, say, to Python: type annotations are ignored at runti…

> A typescript compiler does not generate code

Except for where it does: Enums, namespaces, parameter properties, etc.

Re: Node.js is able to execute TypeScript files without additional configuration

#30

Post by ninetyninenine »

nosianu wrote: post #25
ninetyninenine wrote: post #6

Is there any movement in the node world for the runtime to be able to ascertain types? Obviously nodejs doesn't do this, but does Bun or Deno or are there plans for any of this in the future?

This has nothing to do with the "node world". Such an enormous feature would have to go into ECMAScript. Which is very, very unlikely to ever happen, they may as well design a new language. All those runtimes implement that spec. Expecting them to write an extremely complex new feature that is easily more complicated than everything already implemented (especially with backwards compatibility, and given that the lang…

Can't be too hard imo. Primitives can contain an extra metadata field for the types defined in the code. This doesn't really interfere with the runtime and will be backwards compatible. The runtime of course still doesn't actually have to do any type checking, it's just forwarding the type information on a new metadata field so it's not in any way interrupting the core flow of the runtime logic. As a result you can still have the wrong type tagged onto a primitive just like TS has it currently.

Only downside I see is that It can slow down the code as the runtime now has to evaluate type level functions in order to know what to place in the metadata.

But you're right in the sense that it has to go into the core ECMA specification rather then being a node project.

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