JSJ 399: Debugging with Async/Await with Valeri Karpov
JavaScript Jabber10 Loka 2019

JSJ 399: Debugging with Async/Await with Valeri Karpov

Valeri Karpov is a maintainer on Mongoose, has started a few companies, and works for a company called Booster Fuels. Today’s topic debugging with Async/Await. The panel talks about some of the challenges of debugging with Async. AJ, however, has never encountered the same problems, so he shares his debugging method. Valeri differentiates between .catch vs try...catch, and talks about why he prefers .catch. There are two ways to handle all errors in an async function without leading to an unhandled promise rejection. The first is to wrap the entire body of the async function in a try...catch, has some limitations. Calling an async function always returns a promise, so the other approach is calling .catch on the promise to handle any errors that occur in that function body. One of the key differences is if you return a promise within an async function, and that return promise is wrapped in a try...catch, the catch block won’t get called if that promise is rejected, whereas if you call .catch on the promise that the function returns, you’ll actually catch that error. There are rare instances where this can get tricky and unintuitive, such as where you have to call new promise and have resolve and reject, and you can get unexpected behavior.The panel discusses Valeri’s current favorite JS interview question, which is, “Given a stream, implement a function called ‘stream to promise’ that, given a stream, returns a promise that resolves to the concatenation of all the data chunks emitted by the stream, or rejects if the stream emits an error event.” It’s really simple to get this qustion right, and really simple to get it wrong, and the difference can be catastrophic. AJ cautions listeners to never use the data event except in the cases Val was talking about, only use the readable event.The conversation turns to the function of a readable event. Since data always pushes data, when you get a readable event, it’s up to you to call read inside the function handler, and then you get back a chunk of data, call read again and again until the read returns null. When you use readable, you are in control and you avoid piling functions into RAM. In addition, the right function will return true or false to let you know if the buffer is full or not. This is a way to mix imperative style into a stream.The next discussion topics are the differences between imperative style and reactive style and how a waits and promises work in a normal four loop. A wait suspends the execution of a function until the promise is resolved. Does a wait actually stop the loop or is it just transpiling like a promise and it doesn’t stop the loop. AJ wrote a module called Batch Async to be not as greedy as promise.all but not as limited as other options.The JavaScript panelists talk about different async iterators they’ve used, such as Babel. They discuss the merits of Babel, especially since baseline Android phones (which a significant portion of the population of the world uses) run UC Browser that doesn’t support Babel, and so a significant chunk of the population of the world. On the other hand, if you want to target a large audience, you need to use Babel.Since frameworks in general don’t handle async very well, the panel discusses ways to mitigate this. They talk about different frameworks like Vue, React, and Express and how they support async functions. They discuss why there is no way for you to actually cancel an async option in an actual case, how complex canceling is, and what you are really trying to solve for in the cancellation process. Canceling something is a complex problem. Valeri talks about his one case where he had a specific bug that required non-generic engineering to solve, and cancelling actually solved something. When AJ has come across cancellation issues, it’s very specific to that use case. The rest of the panelists talk about their experiences with having to cancel something. Finally, they talk about their experience with async generator functions. A generator is a function that lets you enter into the function later. This makes sense for very large or long running data sets, but when you have a bounded items, don’t complicate your code this way. When an async generator function yields, you explicitly need to call next in order for it to pick up again. If you don’t call ‘next’, it’s essentially cancelled. Remember that object.keys and object.values are your friends. Panelists
  • Christopher Buecheler
  • AJ O’Neal
  • Charles Max Wood
With special guest: Valeri KarpovSponsorsLinks Follow DevChatTV on Facebook and Twitter PicksAJ O’Neal:Christopher Buecheler:Charles Max Wood:Valeri Karpov:Special Guest: Valeri Karpov.

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030 JSJ Learning & Teaching JavaScript with Noel Rappin

030 JSJ Learning & Teaching JavaScript with Noel Rappin

PanelNoel Rappin (twitter github blog) Jamison Dance (twitter github blog) Charles Max Wood (twitter github Teach Me To Code Intro to CoffeeScript) AJ O’Neal (twitter github blog) Discussion 00:52 - Works in training and talent development for Groupon00:56 - Author of Rails Test Prescriptions and upcoming Master Space and Time with JavaScript01:21 - Writing a book about JavaScript02:33 - Focus of the bookPart 1: Jasmine and jQuery and the JavaScript Object Model Part 2: Extended examples of jQuery Part 3: Backbone Part 4: Ember 03:46 - Self-published authors05:15 - Approaches and mindsets to learning JavaScript06:04 - “Gotchas!” and bad features in Javascript09:17 - Modeling JavaScript for beginners11:23 - (AJ joins the podcast)11:42 - Resources/Classes for learning JavaScriptGood Parts Book: Douglas Crockford JavaScript Patterns: Stoyan Stefanov Eloquent JavaScript: A Modern Introduction to Programming: Marijn Haverbeke Maintainable JavaScript: Nicholas C. Zakas 13:54 - Hiring people with JavaScript experience at Groupon15:12 - Training workshops17:00 - Getting new hires up to speed quicklyPairing Mentoring Lectures Workshops 21:38 - Book LearningYou can learn at your own pace But it’s hard to ask questions to a book 22:51 - How Noel gained expertise in JavaScript24:38 - Code reading and learning to program a language26:18 - Teaching people JavaScript as their very first language31:55 - Classroom layout33:42 - Online trainingKahn Academy Computer ScienceCode AcademyStarter League40:00 - Finding a mentorStack Overflow PicksShrines by Purity Ring (Jamison) Learnable Programming: Bret Victor (Jamison) Mob Software: Richard P. Gabriel & Ron Goldman (Jamison) Monoprice.com (AJ) ZREO: Zelda Reorchestrated (AJ) The Official Twitter App (Chuck) Fluid App (Chuck) Try Jasmine! (Noel) Justin Searls (Noel) The Atrocity Archives: Charles Stross (Noel) Futurity: A Musical by The Lisps (Noel) Transcript NOEL: I’m trying to figure out where the chat is in this stupid Skype interface.JAMISON: Just imagine the worst place it could possibly be and that’s where it is.[This episode is sponsored by ComponentOne, makers of Wijmo. If you need stunning UI elements or awesome graphs and charts, then go to wijmo.com and check them out.][Hosting and bandwidth provided by The Blue Box Group. Check them out at bluebox.net]CHUCK: Hey everybody and welcome to Episode 30 of the JavaScript Jabber show! This week on our panel we have, Jamison Dance.JAMISON: Hey guys!CHUCK: I’m Charles Max Wood from devchat.tv and this week, we have a special guest and that’s Noel Rappin!NOEL: Hey everybody!CHUCK: For the people who don’t know who you are, you want to introduce yourself, Noel?NOEL:  Sure. I currently work in training and talent development for Groupon. And I am the author of previously “Rails Test Prescriptions” and currently a self-published book called “Master Time and Space with JavaScript”, which you can get at noelrappin.com. I need to spell that out, right? N-o-e-l-r-a-p-p-i-n.comCHUCK: So I’m little curious, before we get into the topic which is learning and teaching JavaScript, how did you get into writing a book about JavaScript? What’s your background there?NOEL: You know, it actually relates to teaching and learning JavaScript. I think, I was like… a lot of long time web devs. I spent my first round as a web consultant in around, turn of the century 2000’s. I spent time trying to talk clients out of JavaScript stuff because it was such a pain in the neck. And I kind of got away from it for awhile and came back a couple of years ago to realize that basically, everything had changed and they were actually usable tools now.And last summer, I was working with a… at that time,Special Guest: Noel Rappin. Support this podcast at — https://redcircle.com/javascript-jabber/donationsPrivacy & Opt-Out: https://redcircle.com/privacyBecome a supporter of this podcast: https://www.spreaker.com/podcast/javascript-jabber--6102064/support.

4 Loka 201251min

029 JSJ Bower.js with Alex MacCaw and Jacob Thornton

029 JSJ Bower.js with Alex MacCaw and Jacob Thornton

PanelAlex MacCaw (twitter github blog) Jacob Thornton (Fat) (twitter github blog) AJ O’Neal (twitter github blog) Jamison Dance (twitter github blog) Joe Eames (twitter github blog) Charles Max Wood (twitter github Teach Me To Code Intro to CoffeeScript) DiscussionBower.js (web) Bower.js (twitter) Bower.js (github) SXSW Package managers ender-js BPM hem Benefits Small components Yeoman.io Browserify Dependencies Segmenting the community Transports Mozilla (github) Commands Building an actual package manager node.js Moving parts of a package manager Events Challenges Ember.js Mobile web application development Google Chrome apps Desktop apps in JavaScript PicksKershaw Ken Onion Tactical Blur Folding Knife (AJ) The xx: Coexist (Jamison) Neil Armstrong’s Solemn but Not Sad Memorial Cathedral (Jamison) Collective Soul Cat (Jamison) Amazon Prime (Joe) Star Trek Original Series on Amazon Prime (Joe) Functional Programming Principles in Scala: Martin Odersky (Joe) Domo (hiring!) (Joe) Delegation in Google (Chuck) Civilization IV (Chuck) Fujitsu ScanSnap (Chuck) Bill Nye’s Twitter Account getting suspended was not cool (Jacob) Github + Twitter profile redesign (Jacob) Avoid 7/11 Hot Dog Flavored Chips (Jacob) The Big Picture (Alex) CoffeeScriptRedux (Alex) Stripe (Alex) Special Guests: Alex MacCaw and Jacob Thornton. Support this podcast at — https://redcircle.com/javascript-jabber/donationsPrivacy & Opt-Out: https://redcircle.com/privacyBecome a supporter of this podcast: https://www.spreaker.com/podcast/javascript-jabber--6102064/support.

2 Loka 201247min

028 JSJ Greenfield vs Brownfield Projects

028 JSJ Greenfield vs Brownfield Projects

PanelJoe Eames (twitter github blog) AJ O'Neal (twitter github blog) Jamison Dance (twitter github blog) Charles Max Wood (twitter github Teach Me To Code Rails Summer Camp) DiscussionGreenfield - Brand New Project Brownfield - Older Applications, Legacy Code Poopfield - PHP Development Dealing With Legacy Code Use Tests Working Effectively with Legacy Code - Michael Feathers Risk When is the big rewrite the correct answer? PicksJoseph Smith: Rough Stone Rolling (AJ) Roll Up Crepes (AJ) Calepin (AJ) Bernie (Jamison) Dota 2 (Jamison) Derrick Storm Novels - A Brewing Storm, A Bloody Storm, A Raging Storm (Joe) Castle (Joe) X-Wing Mineatures (Joe) PEX For Fun (Joe) MLG Championship - Starcraft Duel (Joe) VESA 75 to 100 Adapter (Chuck) LG Tone Bluetooth Headphones (Chuck) Transcript JOE: Listen baby, it won’t get weird.JAMISON: [Chuckles]AJ: That sounds... weird.JAMISON: [Chuckles] Too Late.[Hosting and bandwidth provided by the Blue Box Group. Check them out at bluebox.net.][This episode is sponsored by Harvest. I use Harvest to track time, track subcontractor’s time and invoice clients. Their time tracking is really simple and easy to use. Invoicing includes a ‘pay now’ function by credit card and PayPal. And you can sign up at getharvest.com. Use the code RF to get 50% off your first month.]CHUCK: Hey everybody and welcome to episode 28 of the JavaScript Jabber show. This week on our panel, we have AJ O’Neil.AJ: Yo, yo, yo comin’ at you live from the second story of an office base in Orem, Utah.CHUCK:  We also have Jamison Dance.JAMISON: Hi, I’m Jamison Dance and I am super excited, because today iTV just announced that we are doing the Nintendo TV thing; and I haven’t been able to talk about it for, like, six months, so it’s a good day.CHUCK: Cool. We also have Joe Eames.JOE: Comin at you semi live from American Fork, Utah.CHUCK: And I am Charles Max Wood from devchat.tv. Tim is not with us this week because he is in China. I thought I’d point that out, because I think it’s cool. Anyway, this week we are going to be talking about Greenfield versus Brownfield projects. It was kind of funny when we were getting ready to do this, some of the panels were like, Green/Brown?JAMISON: Yeah, I have to pull Josh Susser and ask for a definition.CHUCK: So, as far as I understand it, there are some new --- to this, depending to who you talk to, but mostly, Greenfield is a brand new project with few or no decisions made and no code written for it yet. And Brownfield projects are effectively older applications usually associated with legacy code. You know, so it’s an application that already has code written toward it. Typically, it is out there in the world doing whatever it is supposed to do.JAMISON: Now, I want to put this question delicately. Are there any fecal connotations to the color ‘brown’ in Brownfield?CHUCK: Only if it’s PHP.JOE: [Chuckles]. Then it’s Poopfield Development?CHUCK: [Chuckles]. Okay, we are not gonna go down that tangent.[Laughter]AJ: Because, I mean honestly, when Mormons make jokes about crap, it never sounds good anyway.CHUCK: Yeah. So anyway, how many of you guys have actually worked on a real Greenfield project? Like been there from day one, that you have it just built yourself.JAMISON: I guess it depends on your definition. Maybe. So we have lots of services at ITV, so I've been part of spinning up completely new services that didn’t exist. We had other sort of similar things already, so some of the decisions were already made for, so we kind of had a style established. But it was still like a separate project.AJ: Do you forget us so soon, Jamison?JAMISON: [Chuckles].AJ: You don’t remember ever working here or getting started…JAMISON: I do. I don’t remember Greenfield stuff; I remember new features, I mean, Support this podcast at — https://redcircle.com/javascript-jabber/donationsPrivacy & Opt-Out: https://redcircle.com/privacyBecome a supporter of this podcast: https://www.spreaker.com/podcast/javascript-jabber--6102064/support.

21 Syys 201214min

027 JSJ The JavaScript Community

027 JSJ The JavaScript Community

The panelists discuss the JavaScript community at large. Support this podcast at — https://redcircle.com/javascript-jabber/donationsPrivacy & Opt-Out: https://redcircle.com/privacyBecome a supporter of this podcast: https://www.spreaker.com/podcast/javascript-jabber--6102064/support.

5 Syys 201249min

026 JSJ Code Organization and Reuse

026 JSJ Code Organization and Reuse

The panelists talk about code organization and reuse. Support this podcast at — https://redcircle.com/javascript-jabber/donationsPrivacy & Opt-Out: https://redcircle.com/privacyBecome a supporter of this podcast: https://www.spreaker.com/podcast/javascript-jabber--6102064/support.

28 Elo 201256min

025 JSJ Require.js with James Burke

025 JSJ Require.js with James Burke

The panelists talk to James Burke about Require.js.Special Guest: James Burke . Support this podcast at — https://redcircle.com/javascript-jabber/donationsPrivacy & Opt-Out: https://redcircle.com/privacyBecome a supporter of this podcast: https://www.spreaker.com/podcast/javascript-jabber--6102064/support.

21 Elo 201235min

024 JSJ Strata.js with Michael Jackson

024 JSJ Strata.js with Michael Jackson

Support this podcast at — https://redcircle.com/javascript-jabber/donationsPrivacy & Opt-Out: https://redcircle.com/privacyBecome a supporter of this podcast: https://www.spreaker.com/podcast/javascript-jabber--6102064/support.

14 Elo 201243min

023 JSJ Phantom.js with Ariya Hidayat

023 JSJ Phantom.js with Ariya Hidayat

The panelists talk to Ariya Hidayat about Phantom.js.Special Guest: Ariya Hidayat. Support this podcast at — https://redcircle.com/javascript-jabber/donationsPrivacy & Opt-Out: https://redcircle.com/privacyBecome a supporter of this podcast: https://www.spreaker.com/podcast/javascript-jabber--6102064/support.

7 Elo 201240min

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