new.targetメタプãƒãƒ‘ティã«ã¤ã„㦠- JS.next
æ¦‚è¦ ã€Œnew.targetã€ã¨ã¯ã€ES2015ã§å°Žå…¥ã•ã‚ŒãŸãƒ“ルトインクラスã®ã‚µãƒ–クラスを作る上ã§æ¬ ã‹ã›ãªã„å˜åœ¨ã§ã‚ã‚‹[[newTarget]]ã‚’å–å¾—ã™ã‚‹ãŸã‚ã®ãƒ¡ã‚¿ãƒ—ãƒãƒ‘ティã§ã‚る。 従æ¥ã®å•é¡Œç‚¹ ES5ã¾ã§ã¯Arrayã®ã‚ˆã†ãªãƒ“ルトインクラスをé©åˆ‡ã«ç¶™æ‰¿ã—ãŸã‚µãƒ–クラスを作るã“ã¨ãŒã§ããªã‹ã£ãŸã€‚ ES2015ã‹ã‚‰ã®ãƒ—ãƒãƒˆã‚¿ã‚¤ãƒ—è¨å®šæ©Ÿèƒ½ã‚’使ã†ã¨å¯èƒ½ã§ã‚ã‚Šã€ã“ã®ã‚ˆã†ã«ãªã‚‹ã€‚ class Stack extends Array { constructor( ...args ) { var stack = new Array( ...args ) return Object.setPrototypeOf( stack, Stack.prototype ) } clear() { this.length = 0 } } ã—ã‹ã—毎回ã“ã®ã‚ˆã†ã«æ›¸ã‹ãªã„ã¨ã„ã‘ãªã„ã®ã¯ã‚¹ãƒžãƒ¼ãƒˆã§ã¯ãªã„。 ã§ãã‚Œã°ã“ã®æ§˜ã«æ›¸
V8 JavaScript engine
Show navigationWhat is V8?V8 is Google’s open source high-performance JavaScript and WebAssembly engine, written in C++. It is used in Chrome and in Node.js, among others. It implements ECMAScript and WebAssembly, and runs on Windows, macOS, and Linux systems that use x64, IA-32, or ARM processors. V8 can be embedded into any C++ application. Latest posts and feature explainersIntroducing the WebA
ユニコードエスケープシーケンスãŒæ‹¡å¼µã•ã‚ŒãŸ - JS.next
æ¦‚è¦ ä»Šã¾ã§ã¯ã‚µãƒã‚²ãƒ¼ãƒˆãƒšã‚¢ã«ã‚ˆã‚‹æ–‡å—を１シーケンスã§è¡¨ã™ã“ã¨ãŒå‡ºæ¥ãªã‹ã£ãŸãŒã€ES2015ã§ã¯ã€Ž\u{xxxxx}ã€ã®å½¢å¼ã§ã€Œ0xffffã€ã‚’超ãˆã‚‹æ–‡å—コードを表ã™ã“ã¨ãŒã§ãる。 例 var s1 = '\ud842\udf9f' var s2 = '\u{20b9f}' console.log( s1 == s2, s1, s2 ) // true "𠮟" "𠮟" 実装ã•ã‚Œã‚‹ãƒãƒ¼ã‚¸ãƒ§ãƒ³ V8　3.31.38（文å—列リテラル内）　4.2.1（æ£è¦è¡¨ç¾ãƒªãƒ†ãƒ©ãƒ«å†…）
@@toStringTagãŒå®Ÿè£…ã•ã‚ŒãŸ - JS.next
æ¦‚è¦ ä¾‹ãˆã°ã€ŽObject.prototype.toString.call([])ã€ã¨å‘¼ã¶ã¨ã€ã€Ž"[object Array]"ã€ã¨å¸°ã£ã¦ãã‚‹ãŒã€ ãã®ã€ŒArrayã€ã®éƒ¨åˆ†ã‚’ã©ã†ã„ã†è¡¨è¨˜ã«ã™ã‚‹ã‹è¨å®šã§ãるビルトインシンボルãŒå®Ÿè£…ã•ã‚ŒãŸã€‚ 例 function Cat() { } var cat = new Cat console.log( '' + cat ) // "[object Object]" Cat.prototype[Symbol.toStringTag] = 'Cat' console.log( '' + cat ) // "[object Cat]" 一部ã®ãƒ“ルドインコンストラクタã«ã¯@@toStringTagãŒå®šç¾©ã•ã‚Œã¦ã„る。 console.log( Map.prototype[Symbol.toStringTag] ) // "Map" 実装ã•ã‚Œã‚‹ãƒãƒ¼ã‚¸ãƒ§ãƒ³ V8　3
@@unscopablesãŒå®Ÿè£…ã•ã‚ŒãŸ - JS.next
æ¦‚è¦ withæ–‡ã«ä¸ŽãˆãŸã‚ªãƒ–ジェクトã®ç‰¹å®šã®ãƒ—ãƒãƒ‘ティãŒã‚¹ã‚³ãƒ¼ãƒ—ã«å«ã¾ã‚Œã‚‹ã“ã¨ã‚’防ããŸã‚ã®ã€ ビルトイン"unscopables"シンボルãŒå®Ÿè£…ã•ã‚ŒãŸã€‚ 例 @@unscopablesプãƒãƒ‘ティã®ã‚ªãƒ–ジェクトãŒæœ‰ã™ã‚‹åå‰ã®ãƒ—ãƒãƒ‘ティã¯ã€å€¤ãŒTruthyãªã‚‰ã‚¹ã‚³ãƒ¼ãƒ—ã‹ã‚‰å¤–ã•ã‚Œã‚‹ã€‚ var a = 'unscopable', b = 'unscopable', c = 'unscopable' var obj = { a: 'scopable', b: 'scopable', c: 'scopable', } obj[Symbol.unscopables] = { b: true, c: false } with (obj) { console.log(a, b, c) } /* log "scopable" "unscopable" "scopable" */ 何故必è¦ãªã®ã‹ ES2015ã§
イテレータã«ã¤ã„㦠- JS.next
æ¦‚è¦ V8ã§ES2015ã®ã‚¤ãƒ†ãƒ¬ãƒ¼ã‚·ãƒ§ãƒ³å‘¨ã‚Šã®å®Ÿè£…ãŒé€²ã‚“ã§ããŸã®ã§ã€è§£èª¬ã—ã¦ã¿ã‚ˆã†ã¨æ€ã†ã€‚ イテレーションã¨ã¯ ã“ã“ã§ã¯ãƒ‡ãƒ¼ã‚¿ã®è¦ç´ ã‚’ç¹°ã‚Šè¿”ã—ã¦å–り出ã™ã“ã¨ã€‚ 例ãˆã°é…列ã®forEachメソッドã¯ã€è¦ç´ やインデックスをイテレートã™ã‚‹ã‚¤ãƒ†ãƒ¬ãƒ¼ã‚¿ã§ã‚る。 ãŸã ã—ã“れらã¯ï¼ˆå†…部的ã«ï¼‰ç¹°ã‚Šè¿”ã—ã¾ã§è¡Œã†ã‚¤ãƒ†ãƒ¬ãƒ¼ã‚¿ï¼ˆå†…部イテレータ）ã ãŒã€ES2015ã§ã¯å¤–部イテレーションã®ãŸã‚ã®ä»•çµ„ã¿ãŒå…¥ã£ãŸã€‚ イテレータオブジェクト イテレータオブジェクトã¯ã€Žæ¬¡ã®è¦ç´ ã€ã‚’è¿”ã™ãƒ¡ã‚½ãƒƒãƒ‰ã‚’å‚™ãˆã¦ã„るオブジェクトã§ã‚る。 ã¤ã¾ã‚Šã‚¤ãƒ†ãƒ¬ãƒ¼ã‚·ãƒ§ãƒ³ã®ã€Žæ¬¡ã®è¦ç´ ã‚’å–り出ã™ã€ã“ã¨ã ã‘ã‚’æ‹…ã„ã€ãれを繰り返ã™ã“ã¨ã¯å¤–ã§è¡Œã‚れる（外部イテレータ）。 例 Array.prototype.values()ã¯é…列ã®è¦ç´ ã‚’é †ç•ªã«åˆ—挙ã™ã‚‹ã‚¤ãƒ†ãƒ¬ãƒ¼ã‚¿ã‚ªãƒ–ジェクトを返ã™ã€‚ var ary = [5, 4, 3] var iter = ary.valu
Chromeã®Experimental WebKit/JavaScript Features - fragmentary
追記（2018å¹´4月16日）：ç¾åœ¨ã¯WebKitã§ã¯ãªãBlinkã«ãªã£ãŸãŸã‚“Experimental Web Platform featuresâ€ã¨ã„ã†ã‚»ã‚¯ã‚·ãƒ§ãƒ³ã«ãªã£ã¦ã„る。ã•ã‚‰ã«ã¯ã‚‚ã£ã¨ç°¡å˜ã«ã€runtime_enabled_features.json5ã¨ã„ã†ãƒ•ã‚¡ã‚¤ãƒ«ã‚’見れã°ã©ã‚“ãªæ©Ÿèƒ½ãŒã‚ã‚‹ã®ã‹ãŒã‚ã‹ã‚‹ã‚ˆã†ã«ãªã£ã¦ã„る。 chrome://flagsã«ã¯ã„ã‚ã‚“ãªãƒ©ãƒ³ã‚¿ã‚¤ãƒ フラグãŒã‚る。CSS ShadersやらVP9 playbackやらã€å®Ÿé¨“ä¸ã®æ©Ÿèƒ½ã‚’有効ã«ã§ãるよã†ã«ãªã£ã¦ã„る（動ãã‹ã©ã†ã‹ã¯ã—らãªã„）。 ãã®ä¸ã«ã“ã‚“ãªãƒ•ãƒ©ã‚°ãŒã‚る。 Enable experimental WebKit features. Enable experimental WebKit features that are in development. Enable Experimental JavaS
r24291 - v8 — ES6: Implement object literal property shorthand
You can find more information on our Wiki at http://www.v8project.org
Opera's Developer Relations Team - Opera 10.60 moves to the beta zone
8 March 2022 by Danny Yao in Blog By supporting the Opera Crypto Wallet, Dapp developers can gain access to millions of crypto users on Opera platform. To do so, Dapp developers need simply add a few lines of code to set up integration with the Opera Crypto Wallet. 23 January 2019 by Daniel Bratell in Blog Opera 58 (based on Chromium 71) for Mac, Windows, Linux is out! To find out what’s new for u
13 JavaScript Performance Tips
Daniel Clifford recently gave a great talk at Google I/O 2012 called “Breaking the JavaScript Speed Limit with V8â€. In it he goes in depth to explain 13 simple optimizations you can do in your JavaScript code to help Chrome’s V8 JavaScript engine compile / run your JavaScript code faster. In the talk he gives a lot of great explanations as to what they are and why they help, but if you just want t
New community features for Google Chat and an update on Currents
Join the official community for Google Workspace administrators In the Google Cloud Community, connect with Googlers and other Google Workspace admins like yourself. Participate in product discussions, check out the Community Articles, and learn tips and tricks that will make your work and life easier. Be the first to know what's happening with Google Workspace. ______________ Learn about more Goo
The Future of JavaScript – take a peek today!
$200K 1 10th birthday 4 abusive ads 1 abusive notifications 2 accessibility 3 ad blockers 1 ad blocking 2 advanced capabilities 1 android 2 anti abuse 1 anti-deception 1 background periodic sync 1 badging 1 benchmarks 1 beta 83 better ads standards 1 billing 1 birthday 4 blink 2 browser 2 browser interoperability 1 bundles 1 capabilities 6 capable web 1 cds 1 cds18 2 cds2018 1 chrome 35 chrome 81
Mozilla's NodeConf talk
This document discusses adding a V8 API to SpiderMonkey, Mozilla's JavaScript engine. It aims to give SpiderMonkey a better C++ API like V8's and support evolving JavaScript features. Key points discussed include giving SpiderMonkey a "C++ the good parts" API like V8, supporting upcoming ES.next features like let/const, and exploring proposals for Harmony like arrow functions and classes. Examples
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https://bugs.chromium.org/p/v8/issues/detail?id=3886
d21fd15467e16f185e511dbfbaeef7caddfe804a - v8/v8 - Git at Google
Memory issues with +new Date() and animations
https://bugs.chromium.org/p/v8/issues/detail?id=2599
GitHub - plv8/plv8: V8 Engine Javascript Procedural Language add-on for PostgreSQL
https://bugs.chromium.org/p/v8/issues/detail?id=1913
164 - Wrong order in Object properties interation - v8 - Monorail
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