ecma262
proposal-pattern-matching
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ecma262
- TC39: Add Object.groupBy and Map.groupBy
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The "well-known" Symbols in JavaScript
These aren't valid JavaScript (@@iterator would throw an error). They are actually internal Symbols used in JavaScript. They are used to implement features like iteration, instanceOf, and such internally. They actually might get removed or changed
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📦🔓Closures in JavaScript decoded
Note that in previous editions, the ECMAScript® Language Specification used the term "lexical environment" before it decided to rename it to "Environment Record" so you might encounter this term in other definitions and tutorials.
- Document.all Willful Violation
- ES2023 Candidate source code + specification
- ES2023 candidate source code + spec
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The Evolution of JavaScript
For a new specification to be written, you need two things, a_ technical committee_, and a standard. The standard specification for JavaScript is called ECMA-262, and the technical committee is Technical Committee-39(TC39).
- Why Async/Await Is More Than Just Syntactic Sugar
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Show HN: We are trying to (finally) get tail-calls into the WebAssembly standard
4. Proposed something else [ https://github.com/tc39/proposal-ptc-syntax ]
While apple is against Syntactic tail calls, they’re mainly just opposed to versions of it that would remove/unrequire the tail-call optimisation they already do: https://github.com/tc39/ecma262/issues/535
For the version of it that is backwards compatible, they wouldn’t need to do anything other than recognise it as valid syntax. Their main concern is that it "could add confusion with very little benefit."
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What happened to proper tail calls in JavaScript? (2021)
The spec for STC has a critique of PTC:
- performance
- developer tools
- Error.stack
- cross-realm tail calls
- developer intent
See: https://github.com/tc39/proposal-ptc-syntax#issues-with-ptc
Apple's 2016 response as to why they won't implement STC is here: https://github.com/tc39/ecma262/issues/535
- STC is part of the spec and will take too long to change.
- Now that they've implemented support for PTC, they don't want to regress web pages that rely on it.
- They don't want to discourage vendors from implementing PTC by agreeing to STC.
- They don't want to introduce confusion.
Some of these arguments about confusion and delays seem wrong hindsight, since on every point things would have been better if they'd just agreed to the compromise of STC.
- It would have been part of the spec years ago
- STC would have had a clear way for web pages to know when tail calls could be relied on (and PTC would have been optional)
- Other vendors didn't implement PTC in any case, despite no agreement on STC
- There's even more confusion as things are now
proposal-pattern-matching
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Coming to grips with JS: a Rubyist's deep dive
Note, however, that there is a proposal to add pattern matching to JS.
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Level up your Typescript game, functionally - Part 2
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.
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Building React Components Using Unions in TypeScript
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.
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Explicit Software Design. Preliminary Conclusions
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.
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TypeScript Is Surprisingly OK for Compilers
The proposal for pattern matching syntax seems more akin to what they're looking for.
https://github.com/tc39/proposal-pattern-matching
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[AskJS] C# in every Node.js job posting?
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.
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[AskTS] What do you think will be the future of runtime type checking?
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?
- Updates from the 96th TC39 meeting
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Mostly adequate guide to FP (in JavaScript)
Both are active tc39 proposals :)
https://github.com/tc39/proposal-pipeline-operator - Stage 2
https://github.com/tc39/proposal-pattern-matching - Stage 1
Hopefully we get both in the next couple of years.
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CoffeeScript for TypeScript
We often add promising TC39 proposals into Civet so people can experiment without waiting.
We've added https://github.com/tc39/proposal-pipeline-operator, a variant of https://github.com/tc39/proposal-pattern-matching, a variant of https://github.com/tc39/proposal-string-dedent and others.
Since our goal is to be 99% compatible with ES we'll need to accommodate any proposals that become standard and pick up anything TC39 leaves on the table (rest parameters in any position, etc.)
What are some alternatives?
spec - WebAssembly specification, reference interpreter, and test suite.
fp-ts - Functional programming in TypeScript
proposal-ptc-syntax - Discussion and specification for an explicit syntactic opt-in for Tail Calls.
package.elm-lang.org - website for browsing packages and exploring documentation
TypeScript - TypeScript is a superset of JavaScript that compiles to clean JavaScript output.
content - The content behind MDN Web Docs
io-ts - Runtime type system for IO decoding/encoding
proposal-record-tuple - ECMAScript proposal for the Record and Tuple value types. | Stage 2: it will change!
uwm-masters-thesis - My thesis for my Master's in Computer Science degree from the University of Wisconsin - Milwaukee.
proposal-pipeline-operator - A proposal for adding a useful pipe operator to JavaScript.
telegraf - Modern Telegram Bot Framework for Node.js
await-to-js - Async await wrapper for easy error handling without try-catch