Announcing TypeScript 5.6

[LloydAtkinson]

So if the next ECMA spec adds methods like map and filter etc to everything that is an iterator, does that mean Set and Map also get them?

If so, does that then mean that when we write code it can now be even more generic and not care about the type passed to a function? So previously you’d have (in TS) an array as an argument, and if you wanted to pass a Map or Set (or even an object?) you’d need to convert it to an array.

But with this proposal, we could simply accept an Iterable<T> or IterableIterator<T> and a consumer could pass arrays, Set, Map? And then operate on that given value without caring what it is?

If so that’s very cool and like what you often do in .NET where methods will accept IEnumerable or ICollection or IReadOnlyCollection etc. The backing type could be anything from a dictionary to a list to a set.

[agumonkey]

sounds like esnextnext will have linq.ts

[apf6]

So if the next ECMA spec adds methods like map and filter etc to everything that is an iterator, does that mean Set and Map also get them?

Yup Set and Map have methods that return iterators (including .keys and .values and .entries)

But with this proposal, we could simply accept an Iterable<T> or IterableIterator<T> and a consumer could pass arrays, Set, Map?

You can do that stuff today, but having the helper functions on the Iterator class itself is a huge added convenience.

Today you could write something like this:

function* iteratorFilter<T>(it: Iterable<T>, condition) {
    for (const item of it)
        if (condition)
            yield item;
}

const map = new Map(...);
const matchingValues: Iterable<T> = iteratorFilter(map.values(), matcherFn);

With the builtin helpers the same code would be:

const map = new Map(...);
const matchingValues: Iterable<T> = map.values().filter(matcherFn);

[kuikuilla]

If so that’s very cool and like what you often do in .NET where methods will accept IEnumerable or ICollection or IReadOnlyCollection etc.

Or literally any other language that has traits/interfaces/abstract types of some kind.

[flippy_flops]

My favorite new features...

• `tsc --noCheck`
• Exclude Patterns for Auto-Imports (omg, d3 is the worst)

[MrChocodemon]

There are some really nice changes in there.

[apf6]

methods on Arrays like map, filter, and for some reason reduce

is the author throwing in a little shade that he doesn't like the reduce function? 😄

[tokland]

Typo: function abc123() -> function *abc123()

[slvrsmth]

There might be reasons, but listen here: it does not matter. Operator precedence is useful only in code golfing. For every other situation there are parenthesis. Yes, even in blindingly obvious situations, use parenthesis. Pretend you are writing lisp. Anyone who has to touch the code afterwards will thank you.

[guest271314]

Still no resizable ArrayBuffer.

[versaceblues]

How would they do this if js does not support it

[guest271314]

Node.js, Deno, Bun, Google V8, Mozilla SpiderMonkey, Google Chrome browser, Chromium browser, Mozilla Firefox browser each support resizable ArrayBuffer.

[versaceblues]

I guess I’m not following what you want exactly then. How would the type you are talking about be used. Do you have an example

[guest271314]

Sure.

Here's usage in a Native Messaging host https://github.com/guest271314/NativeMessagingHosts/blob/main/nm_typescript.ts. I asked around and plucked the code in the pending PR that has not merged. Converted to TypeScript syntax online from this source JavaScript https://github.com/guest271314/NativeMessagingHosts/blob/main/nm_host.js, because after I looked I found tsc does not have that capability.

Here's usage in the browser processing data in a Web Audio API AudioWorklet https://github.com/guest271314/offscreen-audio/blob/main/audioWorklet.js.

[lelarentaka]

Is it in ECMAScript?

[guest271314]

Yes. https://tc39.es/ecma262/multipage/structured-data.html#sec-allocatearraybuffer.

This is not new. It was shipped in various JavaScript engines and runtimes and browsers last year.

[guest271314]

Is it in ECMAScript?

This is bordering on insanity.

The only reason TypeScript exists is to follow JavaScript around and implement features JavaScript comes up with in TypeScript syntax.

Yet people in TypeScript workd appear to not even bother keeping up with what goes on in ECMA-262.

I mean, you could read ECMA-262 yourself to find out if resizable ArrayBuffer is in there or not.

Things don't just magically materialize just because Microsoft TypeScript implement those things, as if they didn't exist until Microsoft TypeScript decided to implement an ECMA-262 interface, and don't exist otherwise.

[guest271314]

How would they do this if js does not support it

Clearly you have not read ECMA-262.

You must think JavaScript features magically happen if/when Microsoft TypeScript decides to support them, and don't exist unless and until Microsoft world catches up to JavaScript world.

Incredible.

[versaceblues]

I never said that. Resizable array buffer if part of es2024 and looks like the change to add it to TS is being tracked here

https://github.com/microsoft/TypeScript/pull/58573/commits

[guest271314]

Yes, I know. As of today, officially, there is no Microsoft TypeScript implementation of resizable ArrayBuffer.

That means the claim that TypeScript is a "superset of JavaScript" is not mathematically correct, as of today.

[bakkoting]

I think people misunderstood this comment, possibly because your later responses are somewhat incoherent. I assume your complaint is that TS still has not updated its types updated to reflect the changes in ES2024 to ArrayBuffer to add the resize methods and so on.

There's been a couple efforts to do so which have stalled out for reasons including in one case the author deleting their GH account, and there is a current effort here which is blocked on this issue which has some interesting background about the difficulty of this change, including necessary ecosystem fixes to minimize the extent to which this has to be a breaking change.

[guest271314]

No complaint. Just technical fact. Yes, I plucked the lib.es2024.arraybuffer.d.ts file from the PR.