ES6 Tail Call Optimization Explained · Kyle Owen
From Wikipedia: “A tail call is a subroutine call performed as the final action of a procedure.” return foo(); A tail call optimization may occur when the last thing to evaluate before a function returns is a function invocation. In certain circumstances, the interpreter can the reuse current stack frame for the function call instead of creating a new one. Below I will explain what circumstances a
New regular expression features in ECMAScript 6
RegExp.prototype.exec(str) # If /g is not set, matching always starts at the beginning, but skips ahead until a match is found. REGEX.lastIndex is not changed. const REGEX = /a/; REGEX.lastIndex = 7; // ignored const match = REGEX.exec('xaxa'); console.log(match.index); // 1 console.log(REGEX.lastIndex); // 7 (unchanged) If /g is set, matching starts at REGEX.lastIndex and skips ahead until a mat
ES6 In Depth: Classes – Mozilla Hacks - the Web developer blog
Thanks! Please check your inbox to confirm your subscription. If you haven’t previously confirmed a subscription to a Mozilla-related newsletter you may have to do so. Please check your inbox or your spam filter for an email from us. Cris Mooney Excellent job targeting the experienced JavaScript programmer audience, rather than just those coming from languages with classes already exist and assump
How to know when ES modules are done ~ James Burke
There are few pieces of a module system that need to be available for it to be fully functional. I will describe them here and talk a bit about where ECMAScript (ES) modules seem to be at the moment, from an outside public perspective. I am not on TC-39, the committee that works on the ES language specification (otherwise known as JavaScript, JS). Just someone who has worked on a few JS module sys
気楽にECMAScript 2015したい
最近はOculus Riftとかを主にいじってるわけですけど、いわゆるHTML5も横目でウォッチしていて、たまにJavaScriptを書いたりもします。 で、今風にBabelを使って、かつわりと楽にゆるい感じでECMAScript 2015できるようにしておこうと思って、自分用のテンプレプロジェクトを作りました。Watchify＋Babelify＋BrowserSyncです。 KatsuomiK/ECMAScriptTemplate GitHubからcloneしてnpm installしてnpm run watchすればブラウザが起動して、.jsを書き換えればライブリロードがかかります。MacでもWindowsでも大丈夫のはずです。 package.jsonがこんな感じです。 { "name": "ECMAScriptTemplate", "version": "0.0.0", "desc
Why does forEach throw away the return value while map/filter pass it through unchanged? · Issue #27 · tc39/proposal-observable
I realize map/filter are provisional. But in general it's unclear to me how the return value/exception is supposed to integrate with all this. Another related question is why any thrown exception gets passed through as a promise rejection while the return value gets ignored. Can we use iterator map/filter/forEach to inform the design here? I'm not sure how exactly, but it would be nice, because ri
Use cases for synchronous subscription. · Issue #38 · tc39/proposal-observable
It would be great if we had a list of use cases for synchronous subscription in order to better understand if/when [Symbol.observer] is needed. Please include: Description - Why is this use case important and who are the users. Code - a minimal example demonstrating the use case and showcasing it. preferably codepen/jsbin/jsfiddle but a gist is also fine, demonstrating the issue. Why synchronous s
SIMD型について - JS.next
概要 新しいプリミティブ型であるSIMD型及びAPIがV8で実装されてきている。 SIMDとは、複数の数値を並べて１つの値としたようなデータ型である。 これはCPUによって効率良くサポートされているデータ型であり、 1 + 2 -> 3 をするように [ 1, 2, 3, 4 ] + [ 2, 3, 4, 5 ] -> [ 3, 5, 7, 9 ] を1回の演算ですることができる。 つまり、沢山の数値を扱う場面でSIMD型を利用することで、何倍ものパフォーマンス向上が期待できる。 （※WASMに入ることとなり、ESからは一旦取り除かれました。） 実装される型 float32x4 32bit浮動小数点型を4つ並べた128bitのデータ型 float32はJSの通常のnumberであるところのfloat64より精度が低い int32x4 32bit符号付き整数型を4つ並べた128bitのデータ
Building a property passthrough Higher-Order Component for React - James K Nelson
Just want the component? Find it at GitHub Possibly the most frequently re-implemented code across any React component is that used to pass properties through to child components. This stems from the fact that you generally need some sort of input to make the component useful, while you don’t want these component-specific properties polluting the props on your children. This would be all well and
ES6 In Depth: Proxies – Mozilla Hacks - the Web developer blog
ES6 In Depth is a series on new features being added to the JavaScript programming language in the 6th Edition of the ECMAScript standard, ES6 for short. Here is the sort of thing we are going to do today. <pre> var obj = new Proxy({}, { get: function (target, key, receiver) { console.log(`getting ${key}!`); return Reflect.get(target, key, receiver); }, set: function (target, key, value, receiver)
StrongLoop - An Introduction to JavaScript ES6 Iterators
An Introduction to JavaScript ES6 Iterators by Alex Gorbatchev Jul 16, 2015 / How-To, JavaScript Language Note: This blog post is also available on IBM DeveloperWorks. EcmaScript 2015 (formerly known as ES6) introduces a brand new concept of iterators which allows us to define sequences (limited and otherwise) at the language level. Let us break it down a bit. We are all very well familiar with th
Blog | Traits with ES7 Decorators | CocktailJS
In this post we are going to explore how to use ES7 features to define traits with a brand new module: traits-decorator. ES6 gave us the simplicity to create classes in a more declarative way. With ES6 modules we have also a better and clear definition of what we are exporting. Those aspects were a primary goal of Cocktail. Decorators If you are not familiar with decorators, they are pretty simila
2015-07-14のJS: jQuery 3.0αリリース、JSHintとES.next
JSer.info #236 - jQuery 3.0αがリリースされました。 jQuery 3.0 and jQuery Compat 3.0 Alpha Versions Released | Official jQuery Blog まだα版ですが、.show()と.hide()の仕組みの変更、jQuery.DeferredがPromise/A+互換になり、2.xでdeprecatedとなっていたメソッドの削除などが行われています。 また、以前断念したrequestAnimationFrameによるアニメーションがjQuery 3.0では有効化されています。 .show()と.hide()については以前の挙動に依存したものが多そうなので、α版でどうなるかを試してフィードバックをしてみるといいかもしれません。 A Formal Commitment to New Language Fe
Javascript Async Control Flow
In this post we'll explore an enlightened approach to managing control flow in asynchronous javascript applications. We'll look at powerful new ES6 patterns and the happy future that awaits with ES7. So we are all on the same page, when we discuss control flow we mean the following: Control flow refers to the specification of the order in which the individual statements, instructions or function c
MoscowJS 23 — Процесс стандартизации ECMAScript — Сергей Рубанов
Задумывались ли вы о том, как в языке JavaScript появляется новый функционал? Попробуем разобраться, как пройти путь от черновика предложения до включения в стандарт ECMA-262. Страница доклада — https://moscowjs.org/talks/process-standartizacii-ecmascript/ Все новости и анонсы MoscowJS — в нашем телеграм-канале https://t.me/moscowjs
A Quick Tour Of ES6 (the bits you'll actually use)
Just want examples of ES6 in use? I’ve put four ES6 projects on Github. ES6 has been getting a lot of press lately. And with all of the benefits that the new syntax and built-ins bring, it damn well should. But given the breadth of the changes, how is a forward-thinking developer to know where to start? What is worth practicing now, and what is best left for a rainy day? Well, after spending the l
A Formal Commitment to New Language Features
A Formal Commitment to New Language Features The JSHint team Jul 7th, 2015 In recent months, JSHint has been receiving requests to support proposed JavaScript language features like async/await, method decorators, and class property declarations [1]. The JSHint team has turned down each request, even after the release of ES2015. This has not been easy; as open source project maintainers, nothing g
Seven Surprising JavaScript 'Features'
Over the last couple of months I’ve made a few enhancements to JSHint, mainly as a way of learning ES6 (I’m most proud of re-implementing variable scope detection) and during that process I’ve come across a few things that surprised me, mostly about ES6 but also in ES3, including the following feature, which I’ve never used and this is where I will start. Break from any block You should be aware t
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New in ECMAScript 2016, JavaScript's First Yearly Release
ES6ではデータのプロパティをクラス直下で定義できない - Qiita
