Part 2: JavaScript the Hard Parts: Promises, Async & the Event Loop

Part 2 of JavaScript the Hard Parts: Promises, Async & the Event Loop video lecture with Samantha Salley, Lead Engineer at Codesmith.

During this workshop, you will learn how to master asynchronous JavaScript and promises! Our mental models of asynchronicity in javascript - the event loop, callback queue - are no longer enough. We have to augment them with the new world of native promises and async/await and understand them intuitively. In this session, we’ll do this so you can write readable code and debug effectively.

The workshop will cover:
- The challenge with single-threadedness in JavaScript.
- How asynchronicity enables much of modern web development
- The challenge with asynchronicity in JavaScript and how promises fix the problem of inversion of control

A combination of understanding promises and async/await under the hood and strategies for effective implementation will give you the tools to write clean pro asynchronous code in your work and projects.

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[tusharubale]

That's what is called under the hood !!!! I searched a lot of Youtube videos to understand promises but they explain only syntax. This video completely gives an AHA moment after understanding promises. Thanks Instructor!!!!

[nuej]

Finally, FINALLY I UNDERSTOOD PROMISES. This is the best explanation ever! Well detailed, from scratch, without assuming anything, without the bragging of other youtubers. This is education! Take it from me, a college professor and web developer. You are GREAT, Samantha.

[kimse]

Its a best lecture that i have ever seen on this complex topic
at least this concept is crystal clear now !!! Awesome work Miss

[chp]

This was the most helpful lecture on async JS I've watched. Thanks Samantha!

[jaggyjut]

Great timing as i was finding it hard to understand callbacks and promises. Looking forward to see the async\await video.

[fresh_evgar]

It's just a brilliant explanation that helped me a lot! Thank you, Samantha!

[tony-k]

One of the best videos explaining how async code & promises actually work under the hood.
Thank you!

[lukebusuttil]

Incredible watching this to notice how much essential information is missing from most Promise tutorials ive come across. Annoyed it took me a few videos to remember to check for a Codesmith lecture, have to be some of the best going. Thank you for sharing!

[PedroSilva-rxgg]

These under-the-hood videos are very helpful, thank you!

[daryllmamaril]

Well explained!!! Thank you so much! Really enjoyed this vid!!!

[NathanatUuiu]

Wow, amazing content! Does Codesmith cover Observables and that whole ecosystem so to speak (i.e. Subjects, Observers, BehaviorSubject, etc)? I'd love to learn about this topic from Codesmith since things are explained very well and thoroughly.

[pavankumar-ffbozcy]

What if the callstack is empty and XHR/API request takes longer time to execute before invoking the onfulfillment function carrying the data returned from XHR/API call and placing it in micro task queue? which means micro task queue is also empty and there is a callback function waiting to get executed in the callback queue. What happens here? Does the callback function gets called?

[shkirrr]

I dont really understand the .then part, while this makes the code more predictable, can anyone share any post or something that backs up whats said in this vid that .then pushes callback functions into hidden unFullfillment array?

[justyna]

:/ to havy for me :/ this presentation is for people who knows already very well JS, not for medium_beginners :/I hope I will come back to it one day !