--- title: "This week's JavaScript news, issue 248" publication: "JavaScript Weekly" issue: 248 published_at: "2015-09-04" canonical_url: "https://javascriptweekly.com/issues/248" --- This week's JavaScript news, issue 248 This week's JavaScript news — [Read this e-mail on the Web](http://javascriptweekly.com/issues/248) JavaScript WeeklyIssue 248 — September 4, 2015[Measuring JavaScript Functions' Performance](http://www.sitepoint.com/measuring-javascript-functions-performance/) Peter Bengtsson of Mozilla looks at using the High Resolution Time API’s now() function for performance measurements. SitePoint [ES6 Let, Const and the “Temporal Dead Zone” (TDZ) in Depth](http://ponyfoo.com/articles/es6-let-const-and-temporal-dead-zone-in-depth) A dive into ES6’s new ‘let’ and ‘const’ variable declaration features, how they work, and how ‘let’ operates within the dramatically named _temporal dead zone_. Nicolas Bevacqua [5 Questions Every Unit Test Must Answer](https://medium.com/javascript-scene/what-every-unit-test-needs-f6cd34d9836d) Eric Elliott looks at the essential ingredients for unit tests and explains some of the art behind writing good unit tests first. Eric Elliott [![Frontend Masters\](https://copm.s3.amazonaws.com/47fa5669.png)](https://frontendmasters.com/sale/?utm_source=javascriptweekly&utm_medium=email)[Get Access To 170+ Hours Of Front-End Development Training For $5](https://frontendmasters.com/sale/)14-day $5 trial of front-end training with industry legends. Upgrade for 38% off our original price, or cancel in 10 seconds. Until September 10th at midnight ONLY. See page for details. Frontend MastersSponsor [New React Developer Tools Released](http://facebook.github.io/react/blog/2015/09/02/new-react-developer-tools.html) The React team have released all new, fully rewritten developer tools for the popular library. All written in React themselves, Firefox support, full React Native support, and more. Facebook [webm.js: A JavaScript WebM Video Encoder](https://github.com/Kagami/webm.js) There’s [a demo here.](https://kagami.github.io/webm.js/) Kagami Hiiragi [Angular 2 Survey Results](http://angularjs.blogspot.com/2015/09/angular-2-survey-results.html) An Angular 2 survey got 2100 responses. Opinions on tools and syntax usage were heavily divided, but most Angular 2 users are using TypeScript and WebStorm is the most popular editor. AngularJS Blog [Getting Started with Falcor](https://auth0.com/blog/2015/08/28/getting-started-with-falcor/)[Falcor](http://netflix.github.io/falcor/?utm_source=javascriptweekly&utm_medium=email) is a library from Netflix aiming to change the way webapps request and handle data. Ryan Chenkie [Announcing TypeScript 1.6 Beta](http://blogs.msdn.com/b/typescript/archive/2015/09/02/announcing-typescript-1-6-beta-react-jsx-better-error-checking-and-more.aspx) Introduces a .tsx file extension with support for JSX inside of TypeScript files. Microsoft Jobs - [Front End Developer, Brentwood, TN (onsite, full time)](http://www.daveramsey.com/careers/opportunities?category=Digital+Development)Would you enjoy building websites and digital experiences in HTML, CSS and JavaScript that reach hundreds of thousands of people with a positive message every day? We are looking for a talented Front-End Developer who wants to do Work that Matters. Ramsey Solutions - [Apply to top SF & NYC startups in 60 seconds](https://underdog.io/?utm_source=jsweekly&utm_medium=9_4_2015_jsweeklysponsor&utm_campaign=notimetowaste)Want to spend less time job searching? Sign up to Underdog.io and startup founders & hiring managers will email you directly. You decide where to interview and where to work. Your information is kept private from current & past employers. Underdog.io - [Freelance with Companies like Airbnb, IDEO, JPMorgan](http://www.toptal.com/developers?utm_source=js_weekly&utm_medium=cpm-newsletter&utm_campaign=js_weekly_job)Work with top clients, set your own rates, and work from anywhere as an elite Toptal JavaScript developer. Join the most exclusive network of top software engineers in the world. Toptal In Brief [jQuery Foundation and Dojo Foundation to Merge](http://blog.jquery.com/2015/09/01/jquery-foundation-and-dojo-foundation-to-merge/) news Official jQuery Blog [Tabris.js 1.2 Is Out](http://eclipsesource.com/blogs/2015/09/02/tabris-js-1-2-is-here/?utm_source=jsweekly&utm_medium=email&utm_campaign=jsw1) news tools Mobile Apps with Native UIs from a Single JavaScript Codebase Tabris.JSSponsor [Ember Data v2.0 Released and v2.1 Beta Released](http://emberjs.com/blog/2015/09/02/ember-data-2-0-released.html) news Like Ember 2.0, Data 2.0 is about removing deprecated functionality, not adding new features. Ember.js [Scala.js 0.6.5 Released: The Scala to JavaScript Compiler](http://www.scala-js.org/news/2015/08/31/announcing-scalajs-0.6.5/) news tools Scala.js [The JavaScript Misdirection Contest](http://misdirect.ion.land/) news Can you hide evil code in plain sight? Peter Jaric [Computer Vision with Tracking.js Online Hackathon/Contest](http://levelup1.devpost.com/) news DevPost [How to Test React Native Apps on a Real iPhone](http://blog.bigbinary.com/2015/08/25/how-to-test-react-native-app-on-real-iphone.html) tutorial Chirag Shah [How to Build A Slackbot and Deploy It to Heroku for Absolute Beginners](http://blog.npmjs.org/post/128237577345/how-to-build-a-slackbot-deploy-an-app-to-heroku) tutorial Shivani Negi [ES6 Classes in Depth](http://ponyfoo.com/articles/es6-classes-in-depth) tutorial Nicolas Bevacqua [Defusing Race Conditions when Using Promises](https://quickleft.com/blog/defusing-race-conditions-when-using-promises/) tutorial Alex Johnson [Unimorphic Isoversal JavaScript What?](http://blog.getify.com/unimorphic-isoversal-javascript-what/) opinion Kyle Simpson [10 Essential Sublime Text Plugins for JavaScript Developers](http://www.sitepoint.com/essential-sublime-text-javascript-plugins/) tools SitePoint [Real Time Error Reporting in Minutes. Try Raygun Free for 30 Days](https://app.raygun.io/signup-landing?utm_source=JSNewsletter04&utm_medium=SponsoredLink&utm_campaign=CooperPressSept2015) tools Full stack support detailed diagnostic information lets you resolve errors before they impact your users. RaygunSponsor [Minigrid: Zero-Dependency 2KB Cascading Grid Layout](http://alves.im/minigrid/) code Henrique Alves [Substance: A Library for Web-Based Content Editing](http://substance.io/) code Flexible enough to use simply as-is or to define your own custom editors. Substance Software GmbH [combinatorics.js: Combinatorics JavaScript Library](https://github.com/devanp92/combinatorics.js) code Devan Patel [React CSS Modules: Mapping of Class Names to CSS Modules in React Components](https://github.com/gajus/react-css-modules) code Gajus Kuizinas [Automata.js: Regular Expression to FSM Converter](https://github.com/hokein/Automata.js) code Haojian Wu [Wallop: Minimal Library for 'Showing and Hiding Things'](http://pedroduarte.me/wallop/) code Takes a collection of HTML elements, previous and next buttons, and makes it all work. Pedro Duarte [Bad City: A GTA-style Multiplayer Browser Game Written in JavaScript](http://bad.city/) demo It’s lo-fi and collapses under traffic but.. we've enjoyed this at CooperPress HQ (we might even try joining for a while after sending this issue ;-)). Good luck. Curated by [Peter Cooper](http://twitter.com/peterc) and published by [Cooperpress](https://cooperpress.com/). Like this? 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