proposal-record-tuple VS proposal-pattern-matching

Records and tuples are unlikely to ever ship, or at least are extremely unlikely to ship with the semantics around equality people want. My understanding is that browser vendors already have pretty strong opposition to introducing new primitives at this point. Reading this thread[1] will give some explanation as to the hiccups with how equality would behave. It sucks, because while I wouldn't have expected BigInt to have gotten much adoption in the first place, I constantly run into cases where I'd want records or tuples.

[1] https://github.com/tc39/proposal-record-tuple/issues/387

The next big step is dependent on JS language/runtime features. Specifically the Record-Tuple proposal (https://github.com/tc39/proposal-record-tuple)

TL;DR: It's a way to designate data as being immutable.

JS doesn't currently have a good way to do this, so everything built for it tries to assume that data hasn't changed since it was last set. This leads to headaches for developers and wasted cycles for runtimes.

When JS has a proper way to make data immutable, it makes it easier for libraries/frameworks to make guarantees about the underlying data and makes it possible for runtimes to better optimize code.

relevant issue, which is at the crux of this problem: https://github.com/tc39/proposal-record-tuple/issues/387

There are still so many basic things that aren't in the JS stdlib, though. A good example is Map - if you need to use a tuple of two values as a key, you're SOL because there's no way to customize key comparisons. Hopefully we'll get https://tc39.es/proposal-record-tuple/ eventually, but meanwhile languages ranging from C++ to Java to Python have had some sensible way to do this for over 20 years now.

If you’re reaching for structuredClone, what you really want is native immutable Record and Tuple syntax, and the companion “deep path properties” syntax which allows for efficient and ergonomic immutable updates:

- https://github.com/tc39/proposal-record-tuple

It will be called "record" in JavaScript which will swing the popularity back the other way I guess (currently a language proposal)

I suspect considering the strong desire to maintain consistency with JavaScript, we will eventually see something that when the Record proposal passes through tc39

❗ Where it stands: Still in Stage 1 of the TC39 Pattern Matching Proposal, meaning it’s experimental and far from being implemented in JavaScript yet.

[5] TC39. (2023). ECMAScript Pattern Matching Proposal. Retrieved from https://github.com/tc39/proposal-pattern-matching

Note, however, that there is a proposal to add pattern matching to JS.

There's an ECMAScript proposal that is in the works to add this feature to the language! It's going to look something like this.

More importantly, TypeScript typically commits to build things into itself when the proposal in JavaScript reaches Stage 3. The pattern matching proposal in JavaScript is Stage 1, but depends on many other proposals as well that may or may not need to be at Stage 3 as well for it to work. This particular proposal is interested on pattern matching on JavaScript Objects and other primitives, just like Python does with it’s native primitives. These are also dynamic types which helps in some areas, but makes it harder than others. Additionally, the JavaScript type annotations proposal needs to possibly account for this. So it’s going to be awhile. Like many years.

For true™ functional programming in JS, native pattern matching and partial function application are missing (at least for now: 1, 2). For proper OOP, it lacks real interfaces and compile-time dependency injection.

The proposal for pattern matching syntax seems more akin to what they're looking for.

https://github.com/tc39/proposal-pattern-matching

There's a proposal to add something like that to JavaScript but it's been stuck in limbo since 2017 although there are libraries like ts-pattern which implement it already.

I'll admit, it is easy to assert that the TypeScript language should not be involved in the matters of packages but I also wonder if we're moving towards a point where interfaces will be as common as namespaces and whether or not it would be sensible for the language to incorporate such type assertions into the language formally, after all, it already compiles to various forms of JavaScript and there is a stage 1 proposal submitted to the TC39 committee to give JavaScript pattern matching. If adopted, wouldn't it make sense to allow TypeScript to compile a type into a type guard for the native JavaScript pattern matcher?