ES2021 features list
ES2021 Features! Logical Assignment Operators (&&= ||= ??=) Numeric Separators (1_000) Promise.any & AggregateError String.prototype.replaceAll WeakRefs & FinalizationRegistry Objects Logical Assignment Operators Logical Assignment Operators 📖. //"Or Or Equals" x ||= y; x || (x = y); // "And And Equals" x &&= y; x && (x = y); // "QQ Equals" x ??= y; x ?? (x = y);const updateID = user => { // We c
GitHub - mgechev/is-esm: 🌳 CLI tool which checks if a package is distributed in ECMAScript module format. Helps you reason if the package is tree-shakable.
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ES2020 でリリースされた import.meta について - 30歳からのプログラミング
ES2020 でimport.metaがリリースされた。 この機能を使うと、モジュールのメタ情報を取得することができる。 例えば、当該モジュールのパスを取得することができる。 モジュールのメタ情報を取得する機能であるため、CommonJS や Script モードで使用するとエラーになる。 import.metaでどのような情報を取得できるか、Node.js、Deno、ブラウザで試してみた。 それぞれのバージョンは以下の通り。 Node.js: 14.7.0 Deno: 1.2.2 Google Chrome: 84.0.4147.105 Node.js 前述の通り CommonJS だとエラーになるため、ES Modules で使う必要がある。 // SyntaxError: Cannot use 'import.meta' outside a module console.log(im
TypeScript is JavaScript with syntax for types.TypeScript is a strongly typed programming language that builds on JavaScript, giving you better tooling at any scale.
Package exports | webpack
The exports field in the package.json of a package allows to declare which module should be used when using module requests like import "package" or import "package/sub/path". It replaces the default implementation that returns main field resp. index.js files for "package" and the file system lookup for "package/sub/path". When the exports field is specified, only these module requests are availab
Record & Tuples から派生した JSON.parseImmutable というプロポーザルがよさそう
Records & Tuples というそこそこ有名(?)なプロポーザルがありますが、そのプロポーザルから派生した JSON.parseImmutable という新しいプロポーザルが良さそうなので紹介します。 Records & Tuples Records & Tuples はレコードとタプルという新しいデータ構造を導入する現在 Stage 2 のプロポーザルです。 レコードとタプルは、それぞれイミュータブルなオブジェクトと配列のようなものです。現在提案されている構文では通常のオブジェクトリテラルや配列リテラルの頭に # をつけると、レコードとタプルになります。 const record = #{ x: 1, y: 2, }; const tuple = #[1, 2, 3]; レコードやタプルやイミュータブルなデータ構造なので後から内容を更新することはできません。 レコードとタプルの大
TS 4.7 syntax regression: ';' expected. · Issue #48711 · microsoft/TypeScript
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(This blog post is based on a tweet thread and additional input by Mathias Bynens.) After work started on it in August 2017, May 2022 finally saw the publication of RFC 9239 “Updates to ECMAScript media types” by Matthew A. Miller, Myles Borins, Mathias Bynens, and Bradley Farias. It updates JavaScript MIME type registrations to align with reality: The JavaScript MIME type is now unambiguously tex
GitHub - tc39/proposal-defer-import-eval: A proposal for introducing a way to defer evaluate of a module
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The ECMAScript proposal “Class static initialization blocks” by Ron Buckton is at stage 4 and scheduled to be included in ECMAScript 2022. For setting up an instance of a class, we have two constructs in JavaScript: Field: Create (and optionally initialize) instance properties. Constructor: A block of code that is executed before setup is finished. For setting up the static part of a class, we onl
The changes of proposal’s status @ 98th meeting of Ecma TC39 ECMA-262 New Proposals Proposal Stage Stable Formatting 1 Locale Extensions 1 Iterator Sequencing 1 Joint Iteration 1 Negated in and instanceof operators 1 Updated Proposals Proposal From To RegExp.escape 1 2 Resizable and growable ArrayBuffers 3 4 ECMA-402 New Proposals No Data Updated Proposals No Data This diff is generated by ECMAScr
GitHub - tc39/proposal-atomics-microwait: Micro waits in JS
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ES2022 Preview: 10 Exciting JavaScript Language Features From 2021 JavaScript evolves quickly. In 2021, several proposals have moved to Stage 4 of the TC39 process and will be included in ES2022. They add the following features to JavaScript: Classes and Instances Private instance fields, methods, and accessorsExistence checks for private fieldsPublic static class fieldsPrivate static class fields
What is a realm in JavaScript? 28 Oct 2022 As part of my long term research around browser JavaScript security, in the past year I have been focusing specifically on security for realms ⭐️. Due to the rise of dependencies-based development, the JavaScript ecosystem (and the browser JavaScript ecosystem in particular) is far more vulnerable to what we know as “supply chain attacks” - and the abilit
GitHub - openjdk/nashorn: https://openjdk.org/projects/nashorn
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オプショナルチェーンができるまで 〜仕様と実装〜
オプショナルチェーンができるまで 〜仕様と実装〜 Ross Kirsling ロス・カースリング
ECMAScript proposal “Change Array by copy”: four new non-destructive Array methods
ECMAScript proposal “Change Array by copy”: four new non-destructive Array methods This blog post describes the ECMAScript proposal “Change Array by copy” by Robin Ricard and Ashley Claymore. It proposes four new methods for Arrays and Typed Arrays: .toReversed() .toSorted() .toSpliced() .with() The new methods are for Arrays and TypedArrays # This blog post only demonstrates the new methods with
In this blog post, we take a look at the ECMAScript 2023 feature “Symbols as WeakMap keys” – which was proposed by Robin Ricard, Rick Button, Daniel Ehrenberg, Leo Balter, Caridy Patiño, Rick Waldron, and Ashley Claymore. What are WeakMaps good for? # The key ability of a WeakMap is to associate data with a value: The value is the key of a WeakMap entry. The data is the value of that entry. Consi
【2023/05/05 変更】 ES2023 Change Array by Copy の議論によって Array に追加するメソッドが減り、同様に Tuple から取り除かれた pushed や sorted などの独自メソッドについての記述を削除 Symbols as WeakMap keys が ES2023 となったため修正 0, -0, NaN の等価性、同値性が決まったため修正 JSON.parseImmutable が別提案としてスプリットされたため修正 支持されなかった Box についての記述を削除 JavaScript におけるイミュータブル、ミュータブル JavaScript においてプリミティブはイミュータブル、つまり変更不可能です。 一方でオブジェクトは基本的にミュータブル、つまり変更可能です。Object.freeze を使って凍結することは出来ますが、アクセサプ
Web Developer working on @kintone at @cybozu. Loves JavaScript and Curry! 🍛 Old slides: https://www.slideshare.net/teppeis/presentations
JS Decorators Explained: 10 Years Journey to the Real Implementation | Binary Studio
In 2015, ECMAScript 6 was introduced – a significant release of the JavaScript language. This release introduced many new features, such as const/let, arrow functions, classes, etc. Most of these features were aimed at eliminating JavaScript's quirks. For this reason, all these features were labeled as "Harmony." Some sources say that the entire ECMAScript 6 is called "ECMAScript Harmony." In addi
GitHub - es-meta/esmeta: ECMAScript Specification (ECMA-262) Metalanguage
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Symbol.species に未来はあるのか
いや、ない（反語） ES2015 から導入された @@species について ES2015 からクラス構文が導入され、ビルトインクラスを継承したクラスを簡単に作れるようになりました。 ES2015 を策定するにあたって議論となったのがビルトインクラスそのものを返すメソッドの存在です。例えばこの MyArray のインスタンスで Array#map を実行したときにその返り値は MyArray であるべきでしょうか Array であるべきでしょうか。そしてそれをどうやって Array#map に伝えればいいでしょうか。 これを制御できるようにするのが @@species という Well-known Symbol です。普通は派生クラスを返しますが、任意のクラスを返すように変更することも可能になります。 class MyArray extends Array { // 明示的に @@spe
Design Meeting Notes, 9/22/2021 · Issue #46012 · microsoft/TypeScript
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Proxy のコンストラクタの引数に revoked Proxy を入れたときに TypeError を投げる仕様になっているが、ただ複雑になっているだけで特に意味がないので取りやめる提案。承認された。
GitHub - guybedford/es-module-lexer: Low-overhead lexer dedicated to ES module parsing for fast analysis
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GitHub - engine262/engine262: An implementation of ECMA-262 in JavaScript
While helping develop new features for JavaScript, I've found that one of the most useful methods of finding what works and what doesn't is being able to actually run code using the new feature. Babel is fantastic for this, but sometimes features just can't be nicely represented with it. Similarly, implementing a feature in one of the engines is a large undertaking, involving long compile times an
Scope: TC53 is bringing the benefits of standard software APIs to embedded systems so creators of hardware products can benefit from the same rapid development and scalability long enjoyed by web developers. To achieve that, TC53 is focusing its efforts on ECMAScript®, the programming language of the web. With over twenty years of use at global scale, ECMAScript® has proven able to adapt to indust
GitHub - azu/eslint-cjs-to-esm: ESLint wrapper for migration from CJS to ESM.
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Show navigation The new class static initialization block syntax lets developers gather code that should run once for a given class definition and put them in a single place. Consider the following example where a pseudo-random number generator uses a static block to initialize an entropy pool once, when the class MyPRNG definition is evaluated. class MyPRNG { constructor(seed) { if (seed === unde
This Stage 3 proposal is experimental. Do try it and report bugs; don't use it in production! Temporal Table of Contents Introduction Cookbook API Documentation Temporal.Now Temporal.Instant Temporal.ZonedDateTime Temporal.PlainDate Temporal.PlainTime Temporal.PlainDateTime Temporal.PlainYearMonth Temporal.PlainMonthDay Temporal.Duration Balancing Time Zones Calendars Object relationship String pe
Feature: Using test262 CI data · Issue #10734 · babel/babel
Feature Request: Using our newly added test262 support! test262 is the Official JS conformance tests Mike just wrote a great post about the work behind bringing test262 support to JS parsers (we added it back in 2017). "If JavaScript parsers were also using the project, not only would they become more correct, but they would be better-positioned to contribute tests of their own, so everyone else w
suin・読者3万人『サバイバルTypeScript』公開中！ on Twitter: "ECMAScriptとJavaScriptエンジンとブラウザの関係を図にしてみました。 https://t.co/KiUCqb60xr"
ECMAScriptとJavaScriptエンジンとブラウザの関係を図にしてみました。 https://t.co/KiUCqb60xr
tc39er.us a podcast where we talk to the TC39 delegates about JavaScript and everything else!
GitHub - tc39/proposal-source-phase-imports: Proposal to enable importing modules at the source phase
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Implement the Stage 3 Decorators Proposal by rbuckton · Pull Request #50820 · microsoft/TypeScript
This implements support for the Stage 3 Decorators proposal targeting ESNext through ES5 (except where it depends on functionality not available in a specific target, such as WeakMaps for down-level private names). The following items are not currently supported: --emitDecoratorMetadata, as metadata is currently under discussion in https://github.com/tc39/proposal-decorator-metadata and has not ye
パッケージの移行 パッケージをESMなパッケージとして明示する方法は2つ .mjs の拡張子を使う package.json の type フィールドに module の値を設定する 基本的にパッケージ単位で移行すると思うので、後者の package.json の "type": "module"を設定する。 この設定をすると、パッケージ内のJavaScriptがモジュールのコンテキストで実行されるようになる。 モジュールでは常にstrict modeとなり、Node.jsのESMではrequire、exports、__dirname、__filename などが利用できなくなる。 代わりに、ES2015+のimportとexport文がモジュール構文として利用できるようになる。 JavaScript モジュール - JavaScript | MDN Differences between
![Node.jsライブラリ/ツールをESMに移行する[Node.js 12+]](https://cdn-ak-scissors.b.st-hatena.com/image/square/7e5d02dd4b4470fe1aa0b6dc49fb67aee46c2883/height=288;version=1;width=512/https%3A%2F%2Flh3.googleusercontent.com%2Fa-%2FAOh14Gh5aVg_ccNbbR5jIUsiJw7NuPCWIwaqq1-nXKs5Bw%3Ds250-c)
esm: Unflag --experimental-modules by guybedford · Pull Request #29866 · nodejs/node
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【2024/08/11】 TypeScript の BuiltinIterator が IteratorObject にリネームされたため修正。 【2024/07/28】 TypeScript 5.6 Beta より Iterator Helpers の型サポート BuiltinIterator が入るため、その章を追加。 【2023/10/01】 2023年1月に Async Iterator Helpers が別の提案としてスプリットされ Stage 2 に降格されたため、一部内容を変更。 【2022/12/02】 2022年11月に Stage 3 になったため記事のタイトル、一部内容を変更。 イテレーターのインターフェースについて ES2015 から Symbol.iterator メソッドを持つ Iterable インターフェースを実装したオブジェクトに対して for-of やス
This blog post is about the ECMAScript proposal “Array.fromAsync for JavaScript” by J. S. Choi. It introduces a static method for converting asynchronous iterables to Arrays. Tools for working with synchronous iterables # Currently JavaScript provides several tools for working with synchronous iterables – for example: function* createSyncIterable() { yield 'a'; yield 'b'; yield 'c'; } // Array-de
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JavaScript With Syntax For Types.
RFC 9239: Updates to ECMAScript media types
ES2022 feature: class static initialization blocks
ECMAScript proposal updates @ 2023-09
ES2022 Preview: 10 Exciting JavaScript Language Features From 2021
What is a realm in JavaScript?
ECMAScript 2023 feature: symbols as WeakMap keys
イミュータブルにデータを扱うライブラリと Stage 2 Record & Tuple
Intl.MessageFormat Introduction | ドクセル
2020-02 の TC39 meeting - moriken's project
TC53 - Ecma International
Class static initialization blocks · V8
Temporal documentation
TC39 Podcast
Node.jsライブラリ/ツールをESMに移行する[Node.js 12+]
遅延リストを扱うライブラリと Stage 3 Iterator Helpers
ECMAScript proposal: `Array.fromAsync()`
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