--- title: "This week's JavaScript news, issue 235" publication: "JavaScript Weekly" issue: 235 published_at: "2015-06-05" canonical_url: "https://javascriptweekly.com/issues/235" --- This week's JavaScript news, issue 235 Code smells, essential JS functions, var vs let vs const, and why Babel matters — [Read this e-mail on the Web](http://javascriptweekly.com/issues/235) JavaScript WeeklyIssue 235 — June 5, 2015[JavaScript Code Smells](http://elijahmanor.com/javascript-smells/) A great 30 minute talk by Elijah Manor showing off a variety of code smells (a symptom in source code of other underlying problems) and possible resolutions for them. Elijah Manor [7 Essential JavaScript Functions](http://davidwalsh.name/essential-javascript-functions) Short, useful functions aimed at front-end developers to do things like match a selector, get an absolute URL, or prevent a callback from being called multiple times within a certain timeframe. David Walsh [De Stijl: How Necessary Are var, let, and const?](http://raganwald.com/2015/05/30/de-stijl.html) ES6 lets us use three different explicit variable declaration techniques: var, let and const. Reg digs into their use and sees when they can replace one another. Reg Braithwaite [![Red Gate Software\](http://s3.amazonaws.com/nlga/uploads/item/image/38279/i.gif)](http://www.red-gate.com/products/dotnet-development/ants-performance-profiler/?utm_source=javascriptweekly=displayemail=slowest_code=antsperformanceprofiler=email-23726)[How to find and fix the slowest code in your .NET application](http://www.red-gate.com/products/dotnet-development/ants-performance-profiler/?utm_source=javascriptweekly=displayemail=slowest_code=antsperformanceprofiler=email-23726)Boost the performance of your .NET application with ANTS Performance Profiler. Get rich performance data on your code and database queries to find your application's bottleneck fast. Try ANTS Performance Profiler on your application now. Red Gate SoftwareSponsor [Why Babel Matters](http://codemix.com/blog/why-babel-matters) Babel mostly transpiles ES6 code into ES5 code that can run in today’s browsers, but also performs other optimizations. This post includes a compelling example of why it’s such a big deal. Charles Pick [Predictions On JavaScript in The Next 12 Months](http://javascriptplayground.com/blog/2015/05/the-state-of-javascript/) Jack sees pre-compilation becoming the default, the rise of libraries over frameworks, the popularity of ES7, and more. Jack Franklin [Making Music in the Browser with the Web MIDI API](http://www.keithmcmillen.com/blog/making-music-in-the-browser-web-midi-api/) Enabled in the latest Chrome, the Web MIDI API is here to play with. Here’s a quick look at how to do that from JavaScript. Keith McMillen Instruments [A Tour of Node.js Tools for Visual Studio](http://channel9.msdn.com/Blogs/Seth-Juarez/Nodejs-Tools-for-Visual-Studio) A chat about Visual Studio’s recently improved Node.js support followed by a practical dive into creating a deploying an Express app using VS. _(40 minutes.)_ Channel 9 Jobs - [Apply to the best NYC SF startups in 60 seconds with Underdog.io](https://underdog.io/?utm_source=javascriptweekly=6_5_2015_javascriptweeklysponsor=handpickforyou)We handpick top startups; they connect directly with you. Join now to find a job you’ll love. Underdog - [JavaScript Developer at comScore (Amsterdam, The Netherlands)](http://www.comscore.com/Careers/Job_Opportunities?sfid=18158)[comScore](http://www.comscore.com/) is looking for like-minded developers who are keen to solve interesting UI related problems while working on developing new features and improving their in-house ‘Digital Analytix’ product. comScore - [Top JavaScript Freelancers Wanted (Telecommute)](http://www.toptal.com/javascript?utm_source=cooperpress&utm_medium=newsletter&utm_content=javascript_weekly&utm_campaign=absolute_overfloweth)We only hire the absolute top-tier JavaScript developers and if you survive our utlra-screening™ process, the projects overfloweth. (Must read, write speak English extremely well.) Toptal In Brief [JSON API 1.0 Declared Stable](http://www.cerebris.com/blog/2015/06/04/jsonapi-1-0/) news A specification for APIs that use JSON. Dan Gebhardt [Power Surge: An HTML5 Game Optimization Challenge from Firefox](https://hacks.mozilla.org/2015/06/power-surge-optimize-the-javascript-in-this-html5-game-using-firefox-developer-edition/) news Mozilla Hacks [ES6 In Depth: Destructuring](https://hacks.mozilla.org/2015/05/es6-in-depth-destructuring/) tutorial Mozilla Hacks [Easy AngularJS Forms with angular-formly](https://scotch.io/tutorials/easy-angularjs-forms-with-angular-formly) tutorial Ryan Chenkie [ES7 Function Bind Syntax](http://blog.jeremyfairbank.com/javascript/javascript-es7-function-bind-syntax/) tutorial Jeremy Fairbank [Using Polymer WebComponents with Angular.js](http://jcrowther.io/2015/05/26/using-polymer-webcomponents-with-angular-js/) tutorial Josh Crowther [Detecting Unminifiable Angular Code](https://blog.mariusschulz.com/2015/05/31/detecting-unminifiable-angular-code) tutorial Marius Schulz [Introduction to ES6 Promises: 4 Functions You Need To Avoid Callback Hell](http://jamesknelson.com/grokking-es6-promises-the-four-functions-you-need-to-avoid-callback-hell/) tutorial James K Nelson [An Introduction to Ember.js](https://skillsmatter.com/skillscasts/6362-an-introduction-to-ember-js) video A complete 90 minute live coding exercise. Jamie White [Setting State in React](https://frontendmasters.com/courses/react/setting-state/) video A short video demoing setting state in React -- part of the new course with Ryan Florence. Frontend MastersSponsor [Is ReactJS Really Fast?](http://blog.500tech.com/is-reactjs-fast/) opinion Boris Dinkevich [WatchBench: Build Apple Watch Apps in JavaScript](http://www.alphasoftware.com/watchbench/) tools Seemingly a US only iOS app for now. Alpha Software [Know JavaScript? Build Mobile Apps Using Your Web Skills.](http://www.telerik.com/campaigns/platform/webdev?utm_medium=newsletter=javascriptweeklyr=dc-platform-webdev-mar15=sponsoredlinkjun5) tools AppBuilder combines the tools you need to build, test deploy mobile apps to iOS, Android and Windows Phone. TelerikSponsor [J2C: JavaScript to CSS Compiler](http://j2c.py.gy/) tools code A CSS preprocessor based around JavaScript objects; provides a subset of Sass. Pierre-Yves Gérardy [15 Directives to Extend Your Angular.js Apps](http://codecondo.com/angular-js-directives) tools CodeCondo [JSpreadsheets: A Listing of 31 Open-Source JS Spreadsheets and Data Grids](http://jspreadsheets.com/) tools Handsoncode [Knwl.js: A JavaScript Natural Language Parser](http://loadfive.com/os/knwl/) code Parse text for dates, times, places, phone numbers, and more. LoadFive [Vectorious: Generalized n-Dimensional Matrix & Vector Library](https://medium.com/@mateogianolio/an-introduction-to-vectorious-9c0abc9ab7f0) code tutorial Mateo Gianolio [pdfmake: Client/Server Side PDF Generation/Printing in Pure JS](http://pdfmake.org/) code Based on [PDFKit](http://pdfkit.org/). Bartek Pampuch [SlackBots.js: A Node Library for Running a Slack Bot](https://github.com/mishk0/slack-bot-api) code node Mikhail Mokrushin [Hammer.JS: Add Touch Gestures to Your Pages](http://hammerjs.github.io/) code Has no dependencies and can recognize gestures made by touch, mouse and pointerEvents. Eight Media [irecord: An Immutable Store That Exposes An RxJS Observable](https://github.com/ericelliott/irecord) code A Backbone model with a twist: an immutable object map that exposes an RxJS observable. Good for React. Eric Elliott [EON: Open Source JavaScript Framework for Realtime Dashboards/Maps](http://www.pubnub.com/developers/eon/) code PubNub [console.message: Console Messages for 'Cool Kids'](https://github.com/astoilkov/console.message) code Essentially a bunch of extensions to ‘console’ to print more elaborate messages. Antonio Stoilkov Curated by [Peter Cooper](http://twitter.com/peterc) and published by [Cooperpress](https://cooperpress.com/). Like this? 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