An Introduction to Functors in JavaScript: The Basics in 9 Minutes with Examples 

Why on earth does this video have so little views, that was a great explanation!

Great explains for begineers. Keep doing with live Example. Thank you a lot

So good to finally find an accurate explanation with concrete yet simple examples, thanks!!

I'm glad I found your channel it's a goldmine

This video has extreme value in that it demonstrates scary FP concepts without using FP syntax. It's extremely easy to see what a "functor" is when you can see it in a language most people already understand. Great job and super high production quality skills; wish my tech videos looked this good. What do you use your graphics and how long does it take to put a video like this together?

Coming back to this video to say it is amazing.

Best Functor video. Really simple.

Amazing content, so clearly conveyed with irrelevance omitted. Love it!

Best explanation after two days searching

Okay this is fun. I had a look at Wikipedia article *functor* and was afraid to then watch this video. But having enjoyed and benefitted from other videos you've shared, I worked through this. Pretty sure that I can get this by watching a few more times and writing code following along, grokking all the steps by repeating till the ah~ha arrives. You've done a great job making this approachable. Thank you!

This is the by far the best video on functors.

Congratulations for the clear and easy going explanation! So far the best functor explanation on YT.

This was great. The best explanation of Functors I've ever heard.

The best video that I found about Functors with a great and concise explanation, thank you

This video is invaluable. Thank you for taking your time to explain FP concepts derived from category theory in a demistified, practical and clear way.

this is a very great explanation, thank you!!!

This video was amazing, you totally made the topic more understandable for someone with C#/TS experience wanting to jump to some more functional concepts. Subscribed :)

I actually understand now. Brilliant :) ❤

Thanks so much for this video!

Very nice lesson!

You simply and absolutely should have more subscribers, due to this video alone. However, I skimmed through some of your other videos and your videos are immaculately produced and presented. I love to see it! Props & respect!🥰 SUBSCRIBED!!!!!

Fantastic video! :) thanks!

Great content!

Amazing video ❤, like your style of explanation

Very similar to Brian Lonsdorf content, thank you so much for creating this, clear, concise, and practical!

This video is SO good

Thanks so much for this, it was super helpful

Really nice explanation. I've played around with Haskell and Elm, but never really got the whole Functor, Applicative, Monad business. Having another crack at it and this video is great

Awesome content really love it ! ❤️

Yo I want a series on fp-ts from you The video was great and easy to understand

Nice topics. Thanks mam

Nice content!

Damn, super interesting tutorial!

Excellent, precious video. Would you be so kind to do one about Monads? Please do one on monads. We desperately need one! Thanks 😃

Hi, Ijemma! Thanks for the content, it's earned my Like. I'd like to add a bit to the 'nestedNumbers' vs 'chainedNumbers': indeed, reading chained map() calls is easier and we can plug in trace/tap() for debugging, and certainly looks better than e(g(f(x))). Luckily, FP gives us one more cool feature - compose(). h = compose(e, g, f) . -> map(h)

love it!

Your channles so usefull and to the point. I love it! Thx for the content. BTW your missing a closeing parenthesis on the example at 3.28

this is so cool

damn great video

Functors are funky

Also the other concepts of fp please, like Monads etc. Especially in the context of Typescript

I really enjoyed this video for the content but also the production style. What tool do you use for the animated on-screen content if you don't mind me asking?

these animations!! yes!!!!

This is really funny. This explanation of a Functor is really somewhat different from what I have seen from a C++ tutorial. To me it looks like a specific version of it, not the whole story. In that tutorial a functor was explained as an object that behaves like a function. It did this by directly implementing the function call operator, so that it could literally be called as if it where a real function. And ok, I know JS does not have operator overloading, so then it that map method and that then method are ways to replace that. But this is all not the issue. In that C++ explanation they where NOT talking about that whole identity rule, just about composition. They did not require that the created function should return a new data structure or a new functor, but the generated function was just returning a single value like an integer for example. Was that a wrong explanation? I would say, that identity thing is more important for Monads, which are basically very related, but which indeed require both a wrapped type as imput as well as that they return the that wrapped type (arrays or lists are a good example, but the Option and Result types in the Rust language are also great examples of monads). I am really interested in anyones reply on this, learn me more.

You awesome

wtf, insta sub!

more videos about applicative functor

I too wanna say howdy to Don, Ramy, and Chadwick--Ijemma knows what's up

Quick question: if I map to a different type, such as going from an array of strings to an array of ints, is it still a functor? If I do ["John", "Mary", "Kate"].map(name => name.length), thus changing the inner type, is it still a functor or a different kind of functor?

Calling this a functor is the silliest thing I’ve ever heard in my life

what is functor identity and what are the use cases?

Why are you calling a container data structure a functor. This just seems like a ruse for FP people to sound like they are smarter than everyone else. IMHO.