GitHub - engine262/engine262: An implementation of ECMA-262 in JavaScript
An implementation of ECMA-262 in JavaScript Goals 100% Spec Compliance Introspection Ease of modification Non-Goals Speed at the expense of any of the goals This project is bound by a Code of Conduct. Join us in #engine262:matrix.org. 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 ru
JavaScript: The First 20 Years
JavaScript: The First 20 Years by Allen Wirfs-Brock and Brendan Eich Our HOPL paper is done and submitted to the ACM for June 2020 publication in PACMPL (Proceedings of the ACM on Programming Languages) and presentation at the HOPL 4 conference in June 2021. PACMPL is an open access journal so there isn’t a paywall preventing people from reading our paper. The official version of the paper is a
Top-level awaitとDual Package Hazard - 株式会社カブク
Node.js Advent Calendar 2019の21日目の記事です。 2019/12/25追記 もともと「Top-level awaitによるESモジュールの非同期化とDual Package Hazard」というタイトルにしていましたが、表現に勇み足な部分があり、ご指摘をいただいたので、少し修正しました。 「TLAによってNode.jsのESMが非同期になった」という表現はおそらく正確ではありません。ESMに関する2017年のNode.jsのドキュメントでは、特に理由は触れずに「ESMのロードは非同期で、それはブラウザの挙動と合致する」と記述されています。ここでいう「ブラウザの挙動」とは、WHATWG Loaderで定められた仕様を指すと考えられます。ECMAScriptの仕様としては、少なくとも2019まではESMが非同期であるとの記述はなさそうなので、ブラウザの仕様に合わせ
GitHub - mikeal/reg: Native ESM Package Manager
reg is a package manager for native ES Modules. It's built to enable dependency management for Universal JavaScript (JavaScript that can run in the Browser and in Node.js w/o a compiler). This library is highly experimental and still likely to break without notice. DO NOT USE THIS IN PRODUCTION. Supporting Universal JavaScript is quite difficult as the Browser's module system has a very unique set
Moddable Blog | XS Update
November 14, 2019 | Peter Hoddie, Principal d The latest update to the XS JavaScript engine continues to focus on adapting and optimizing JavaScript for embedded systems. In this release, the majority of these improvements take place during the preload phase, part of the build process. Additionally, this release adds support for top-level await and WeakRef, two new JavaScript features expected to
そろそろJavaScriptに採用されそうなOptional Chainingを今さら徹底解説 - Qiita
みなさん、Optional Chaining使ってますか？ 私は先日出たTypeScript 3.7 Betaを小さいプロジェクトに導入して使ってみました。これはとても快適ですね。 例によって、Optional ChainingはECMAScriptに対するプロポーザルの一つです。つまり、もうすぐ入りそうなJavaScriptの新機能です。プロポーザルはたくさんの種類がありますが、その中でもOptional Chainingはその高い有用性からこれまで多くの注目を集めてきました。Optional Chainingは2019年6月のTC39ミーティングでStage 3に上昇し、いよいよ正式採用が近く期待も高まってきたところです。TypeScript 3.7にも導入されたため、TypeScriptユーザーの方々は11月上旬に正式リリースが予定されているTypeScript 3.7を今か今かと待
Evaluating JavaScript code via `import()`
The import() operator lets us dynamically load ECMAScript modules. But they can also be used to evaluate JavaScript code (as Andrea Giammarchi recently pointed out to me), as an alternative to eval(). This blog post explains how that works. eval() does not support export and import # A significant limitation of eval() is that it doesn’t support module syntax such as export and import. If we use i
GitHub - Agoric/realms-shim: Spec-compliant shim for Realms TC39 Proposal
This repository contains a legacy shim implementation of an outdated Realm API Proposal. The Realms proposal has been superceded by the ShadowRealm Proposal. This shim does not implement ShadowRealm, which (as of this writing) is a proposal at Stage 3 of the TC39 standardization process, so common JS engines should have support soon. We do not recommend the use of this shim or the original Realms
Optional chaining · V8
Long chains of property accesses in JavaScript can be error-prone, as any of them might evaluate to null or undefined (also known as “nullish” values). Checking for property existence on each step easily turns into a deeply-nested structure of if-statements or a long if-condition replicating the property access chain: // Error prone-version, could throw. const nameLength = db.user.name.length; //
Promise.allSettled と Promise.any | blog.jxck.io
Intro Promise.allSettled() と Promise.any() の仕様策定が進んでいる。 両者は近いレイヤの仕様では有るが、作業の進捗には差がある。 Promise.allSettled は Stage 4 であり、Chrome や Safari TP には実装もされている Promise.any は Stage 2 であり、実装はまだない ここでは、これらがあると何が嬉しいのかを Promise.all(), Promise.race() の特徴を踏まえて解説する。 Promise.all()/race() Promise.all(), Promise.race() は、いずれも複数の Promise をまとめて処理する Utility Method のようなものである。 all は全ての Promise が Resolve したら Resolve し、race は
Nullish Coalescing と Optional Chaining | blog.jxck.io
Intro JS における null/undefined の扱いを改善するための 2 つの機能が提案されている。 Nullish Coalescing Operator (stage 3) Optional Chaining Operator (stage 3) いずれも Stage 3 に進み、実装も始まっているので、現時点での解説を行う。 Nullish Coalescing 対象が null/undefined だった場合にデフォルト値を返したいといった場合を考える。 function main(option) { option.param = option.param || 'default' } main({param : 'hello'}) しかし、この場合は null/undefined 以外にも param が 0, false, '' など falsy な値の場合も上書き
ES feature: `globalThis`
Warning: This blog post is outdated. Instead, read section “globalThis” in “Exploring JavaScript”. The ECMAScript proposal “globalThis” by Jordan Harband provides a new standard way of accessing the global object. JavaScript’s global scope # JavaScript’s variable scopes are nested and form a tree whose root is the global scope. That scope is only the direct scope when a script runs in a web brows
Weak references and finalizers · V8
Show navigation Generally, references to objects are strongly held in JavaScript, meaning that as long you have a reference to the object, it won’t be garbage-collected. const ref = { x: 42, y: 51 }; // As long as you have access to `ref` (or any other reference to the // same object), the object won’t be garbage-collected.Currently, WeakMaps and WeakSets are the only way to kind-of-weakly referen
Object.fromEntries · V8
Object.fromEntries is a useful addition to the built-in JavaScript library. Before explaining what it does, it helps to understand the pre-existing Object.entries API. Object.entries #The Object.entries API has been around for a while. Chrome: supported since version 54Firefox: supported since version 47Safari: supported since version 10.1Node.js: supported since version 7Babel: supported For each
Array.prototype.flat and Array.prototype.flatMap · V8
Show navigation Array.prototype.flat #The array in this example is several levels deep: it contains an array which in turn contains another array. const array = [1, [2, [3]]]; // ^^^^^^^^^^^^^ outer array // ^^^^^^^^ inner array // ^^^ innermost arrayArray#flat returns a flattened version of a given array. array.flat(); // → [1, 2, [3]] // …is equivalent to: array.flat(1); // → [1, 2, [3]]The defa
Faster script loading with BinaryAST?
The performance of applications on the web platform is becoming increasingly bottle necked by the startup (load) time. Large amounts of JavaScript code are required to create rich web experiences that we’ve become used to. When we look at the total size of JavaScript requested on mobile devices from HTTPArchive, we see that an average page loads 350KB of JavaScript, while 10% of pages go over the
リリース、障害情報などのサービスのお知らせ
最新の人気エントリーの配信
j次のブックマーク
k前のブックマーク
lあとで読む
eコメント一覧を開く
oページを開く
GitHub - Agoric/SES: MOVED to @agoric/ses-shim. SES (Secure EcmaScript) is a secure runtime for running third-party code safely
GitHub - daumann/ECMAScript-new-features-list: A comprehensive list of new ES features, including ES2015 (ES6), ES2016, ES2017, ES2018, ES2019
JavaScript Promise combinators: `.all()`, `.race()`, `.allSettled()`
GitHub - tc39/proposal-regexp-match-indices: ECMAScript RegExp Match Indices
