JavaScript typeof – LogRocket
A very important aspect of every programming language is its type system and data types. For a strictly typed programming language like Java, variables are defined to be of a particular type, constraining the variable to only contain values of that type. JavaScript, however, is a dynamically typed language, although some extensions exist that support strict typing, such as TypeScript. With JavaScr
レガシーなフロントエンドコードを整理するためにどう立ち向かったか - Misoca開発者ブログ
2エントリ連続でこんにちは、@mugi_unoです。 名古屋には台湾ラーメンイタリアンという名物があるそうです。 富山県民の私には理解が追いつきませんでした。 フロントエンドでの金額計算処理 さて、Misocaは請求書作成サービスなので、金額計算処理が欠かせません。 フロントエンドも例外ではなく、消費税額や合計額を算出するロジックが存在します。 機能変更が必要になった!! 諸事情により、そのロジックに変更を加える必要が生じました。 長くプロダクトを支えてくれていた存在ですが、内容的にはいわゆるレガシーなコードで、たびたび開発者ミーティングでも課題として挙げられることがありました。 git log で確認してみると、該当コードに対しての機能的な変更は2015年の冬から行われていません。 何が問題だったのか？ DOM操作と計算ロジックの混在 Misocaでは、新しくコードを書く際はVueやRe
Idle Until Urgent — Philip Walton
A few weeks ago I was looking at some of the performance metrics for my site. Specifically, I wanted to see how I was doing on our newest metric, first input delay (FID). My site is just a blog (and doesn’t run much JavaScript), so I expected to see pretty good results. Input delay that’s less than 100 milliseconds is typically perceived as instant by users, so the performance goal we recommend (a
Operational Introduction to Algebraic Effects and Continuations
algebraic-effects-series-1.md Algebraic Effects in JavaScript part 1 - continuations and control transfer This is the first post of a series about Algebraic Effects and Handlers. There are 2 ways to approach this topic: Denotational: explain Algebraic Effects in terms of their meaning in mathematics/Category theory Operational: explain the mechanic of Algebraic Effects by showing how they operate
A tour of JavaScript timers on the web
1 Sep A tour of JavaScript timers on the web Posted September 1, 2018 by Nolan Lawson in Web. Tagged: javascript, performance. 14 Comments Pop quiz: what is the difference between these JavaScript timers? Promises setTimeout setInterval setImmediate requestAnimationFrame requestIdleCallback More specifically, if you queue up all of these timers at once, do you have any idea which order they’ll fir
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Introducing F2
F2 is a free and open-source modern charting library, released under MIT license. The aim of F2 is helping developers to create interactive visualizations for mobile devices more easier. F2 is born for mobile, developed for developers as well as designers. It is Html5 Canvas-based, and is also compatible with Node.js, Weex and React Native. Based on the grammar of graphics, F2 provides all the cha
Better tree shaking with deep scope analysis
Here’s my project in GSoC 2018: Improve tree-shaking for webpack, a widely used JS code bundler. IntroductionTree-shaking, a supporting feature for DCE(dead code elimination) to help DCE on cross-module usage, is a crucial feature for a bundler. It's especially true for JS. Reducing the bundle size means reducing the network cost each time a bundle is delivered for web application. Project on Gith
Variable Scope in Modern JavaScript
It often surprises me when speaking to other JavaScript developers how many are unaware of how variable scope works in the language they code in. By scope we are talking about the visibility of variables in our code; or in other words which parts of the code can access and modify a variable. I regularly find people declaring variables with var in the middle of code, not knowing how JavaScript will
ちゃんと理解するCode Splitting - Qiita
Deleted articles cannot be recovered. Draft of this article would be also deleted. Are you sure you want to delete this article? Code Splitting、サボってきたのですが、必要になりそうだったので真面目に調べてみました。 これからCode Splittingやりたい方の入口的な役割になれれば幸いです。 Code Splittingとはなにか Code Splittingはその名の通り「コードを分割すること」を指します。分割されたコードはユーザのアクションに応じて非同期に読み込まれます。 ちなみにWebpackでentry point分けることとかもCode Splittingと言えばそうなのですが、本記事では触れません。また、別にSPAでなくともCode
The Cost Of JavaScript In 2018
Update: The Cost Of JavaScript In 2019 is now available to read. Building interactive sites can involve sending JavaScript to your users. Often, too much of it. Have you been on a mobile page that looked like it had loaded only to tap on a link or tried to scroll and nothing happens? Byte-for-byte, JavaScript is still the most expensive resource we send to mobile phones, because it can delay inter
Logging Activity With The Web Beacon API — Smashing Magazine
The Beacon API is a lightweight and efficient way to log information from a web page back to a server. It is used for sending small amounts of data to a server without waiting for a response. Think of it like a postcard sent home when on vacation. You put a small amount of data on it, put it in the mailbox, and you don’t expect a response. In this article, Drew McLellan will help you find out how
Array.prototype.sort について
JavaScript の配列にはsortメソッドがあり配列のソートを実行することができるけど、この配列のソートの中の実装はどうなっているのかという話。v8 における配列ソートについての記事が大変参考になりました。 Chrome(V8)の実装はarray.jsにあり、配列の要素数が 10 以下の場合はInsertion sortを使い、それ以上の場合はQuicksortを利用する。Insersion sort の計算量は O(n^2)であるけど、少ない要素数の場合は Quicksort などより高速になるらしい。直近の commmitを見る限りだと、Chrome 69 か 70 あたりでTimsortに置き換えるつもりらしい。Timsort は average が O(n log n)で、最悪でも O(n log n)の計算量で済む。Quicksort を TimSort に置き換えるつもり
Page Lifecycle API | Web Platform | Chrome for Developers
Modern browsers today will sometimes suspend pages or discard them entirely when system resources are constrained. In the future, browsers want to do this proactively, so they consume less power and memory. The Page Lifecycle API provides lifecycle hooks so your pages can safely handle these browser interventions without affecting the user experience. Take a look at the API to see whether you shou
What's Happening With the Pipeline (|>) Proposal? · Babel
With the release of babel@7.0.0-beta52, we introduced a new required configuration flag to @babel/plugin-proposal-pipeline-operator, a breaking change for the pipeline operator. To clear up any confusion, let's take a look at the pipeline proposal and why we needed to introduce this configuration option. Current Status The pipeline operator was originally introduced by Gilbert Garza, providing a
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Connection-Aware Components