Barker Library - TE7.N2755 no.522

Barker Library - TE7.N2755 no.542

Online Resource

The synchronisation coincided with Prime Minister Manmohan Singh's three-day visit to Russia.

Warner, Terence E., 1960-

Jabit, Nurul Ain, author

The panelists discuss asynchronous programming.

Pete Hodgson crosses over from the iPhreaks podcasts to talk with the Jabber gang about testing asynchronous Javascript with promises.

The panelists talk to Elliot Kember about asynchronous UI and non-blocking interactions.

Panel:

• Charles Max Wood
• AJ O’Neal
• Aimee Knight

Special Guests: Valeri Karpov 

In this episode, the panel talks with programmer, Valerie Karpov from Miami, Florida. He is quite knowledgeable with many different programs, but today’s episode they talk specifically about Async/Await and Promise Generators. Val is constantly busy through his different endeavors and recently finished his e-book, “Mastering Async/Await.” Check-out Val’s social media profiles through LinkedIn, GitHub, Twitter, and more.

Show Topics:

1:20 – Val has been on previous episodes back in 2013 & 2016.

1:37 – Val’s background. He is very involved with multiple companies. Go checkout his new book!

2:39 – Promises generators. Understand Promises and how things sync with Promises. Val suggests that listeners have an integrated understanding of issues like error handling.

3:57 – Chuck asks a question.

6:25 – Aimee’s asks a question: “Can you speak to why someone would want to use Async/Await?”

8:53 – AJ makes comments.

10:09 – “What makes an Async/Await not functional?” – Val

10:59 – “What’s wrong with Promises or Async/Await that people don’t like it?” - AJ

11:25 – Val states that he doesn’t think there really is anything wrong with these programs it just depends on what you need it for. He thinks that having both gives the user great power.

12:21 – AJ’s background is with Node and the Python among other programs.

12:55 – Implementing Complex Business Logic.

15:50 – Val discusses his new e-book.

17:08 – Question from Aimee.

17:16 – AJ answers question. Promises should have been primitive when it was designed or somewhat event handling.

17:46 – The panel agrees that anything is better than Call Backs.

18:18 – Aimee makes comments about Async/Await.

20:08 – “What are the core principles of your new e-book?” – Chuck

20:17 – There are 4 chapters and Val discusses, in detail, what’s in each chapter.

22:40 – There could be some confusion from JavaScript for someone where this is their first language. Does Async/Await have any affect on the way you program or does anything make it less or more confusing in the background changes?

24:30 – Val answers the before-mentioned question. Async/Await does not have anyway to help with this (data changes in the background).

25:36 – “My procedural code, I know that things won’t change on me because it is procedural code. Is it hard to adjust to that?” – AJ

26:01 – Val answers the question.

26:32 – Building a webserver with Python. 

27:31 – Aimee asks a question: “Do you think that there are cases in code base, where I would want to use Promises? Not from a user’s perspective, but what our preferences are, but actual performance. Is there a reason why I would want to use both or be consistent across the board?”

28:17 – Val asks for some clarification to Aimee’s question.

29:14 – Aimee: “My own personal preference is consistency. Would I want to use Promises in ‘x’ scenario and/or use Async/Await in another situation?”

32:28 – Val and AJ are discussing and problem solving different situations that these programs

33:05 – “When would you not want to use Async/Await?” – AJ

33:25 – Val goes through the different situations when he would not use Async/Await. 

33:44 – Chuck is curious about other features of Async/Await and asks Val.

36:40 – Facebook’s Regenerator

37:11 – AJ: “Back in the day, people would be really concerned with JavaScript’s performance even with Chrome.” He continues his thoughts on this topic.

38:11 – Val answers the AJ’s question.

39:10 – Duck JS probably won’t include generators.

41:18 – Val: “Have anyone used Engine Script before?” The rest of the panel had never heard of this before.

42:09 – Windows Scripting Host

42:56 – Val used Rhino in the past.

43:40 – Val: “Going back to the web performance question...”

47:08 – “Where do you see using Async/Await the most?” – Chuck

47:55 – Val uses Async/Await for everything on the backend because it has made everything so easy for him.

48:23 – “So this is why you really haven’t used Web Pack?” – AJ

49:20 – Let’s go to Aimee’s Picks!

50:18 – AJ’s story, first, before we get to Promises.

54:44 – Let’s transition to Promises Finally.

54:53 – Val talks about Promises Finally.

59:20 – Picks

Links:

• JavaScript
• Valeri Karpov’s GitHub
• Valeri Karpov’s Twitter
• Valeri Karpov’s LinkedIn
• New E-Book: Mastering Async/Await
• Node
• Python
• Windows Scripting Host
• Facebook’s Regenerator
• Rhino

Sponsors:

• Kendo UI
• Sentry
• Digital Ocean
•  

Picks:

Charles

• YouTube Video “IKEA” by Coulton
• Conference
• Amazon Prime Day

Aimee

• Blog Post Article

AJ

• IKEA
• https://ppl.family

Val

• https://www.npmjs.com/package/serve
• http://bit.ly/ultimate-skiing
• http://asyncawait.net/jsjabber
• New E-Book: Mastering Async/Await

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 Karpov

Sponsors

• The DevEd Podcast

• Sentry use the code “devchat” for 2 months free on Sentry’s small plan

• Adventures in DevOps

Links

• Mongoose

• Express 5

• Node Streams

• Pull Streams

• Masteringjs.io

• MongoDB

• Babel

• HTML

• Webpack

• Vue

• Express

• RxJS

• Console.log

• Json.stringify

• Batchasync.js

• How to Write Batch Async Functions

Follow DevChatTV on Facebook and Twitter

Picks

AJ O’Neal:

• Ethan Garofolo YouTube

Christopher Buecheler:

• Functional Design Patterns for Express.js

Charles Max Wood:

• Microsoft Ignite

• Maxcoders.io

Valeri Karpov:

• Follow Valeri on Twitter @code_barbarian and Github @vkarpov15

• Masteringjs.io

• Jurassic Park: A Novel

A 58-year-old woman presents with no relevant medical history with syncope, elevated troponin and D-dimer levels, and multiple large bilateral pulmonary emboli. What would you do next?

This essay describes a physician’s experience of the sudden, unexplained death of her brother and her family’s discovery of the genetic cause.

Cao, Guozhong

Faunce, T

Cao, Guozhong

Shah, Monali, author