What Is Recursion - In Depth

[@quintenkamphuis]

Hi from The Odin Project! I coded along and am very proud to say that I got every single one exactly right.

[@GrantH2606]

Hi from the The Odin Project! I coded along and am not proud to say I am totally lost on understanding recursion and am on the brink of throwing in the towel.

[@fsl72]

@@GrantH2606 did you throw in the towel?

[@GrantH2606]

@@fsl72 I decided to continue despite not understanding recursion

[@fsl72]

@@GrantH2606 so did you skip the recursion-related lessons?

[@GrantH2606]

@@fsl72 no, i went through them all but had to resort to using chatgpt to help me get past it. I just couldn't wrap my head around it.

[@baronfuller3112]

This guy is for sure my go to when needing to learn a topic. Would recommend to anyone.

[@bhuppidhamii]

yes, he truly is!

[@AnnieTaylorChen]

Wow that's smart. I really like the last family-tree example as it makes a lot of sense than pure code. ^^ You truly have the talent to make the newbie-devs' life easier.

[@WebDevSimplified]

Thank you! An example like the last one of nested lists is something I run into fairly often and always reach for recursion when I do.

[@ozzyfromspace]

This is a hundred times better than when my professor tried to teach our class recursion. Boy, that was a train wreck 😂. You're a national treasure, Kyle! Thanks so much for everything you do 🏆☮️🙌🏽🎊

[@kmchow4971]

He is an international treasure.

[@IkeVictor]

i have watched 15 recursion videos and this seems to be the most clear and concise. Congrats, here is your trophy 🏆 .....lol

[@VladdyHell]

Recursion is the most confusing concept aside from asynchronous programming even though I've read from a lot of resources, but you explained it very very well and it's actually very easy, your explanation is just 🔥

[@justinreeves8336]

What makes your videos so good is the thought that goes into creating the examples to explain. So many other authors "showboat" overly complex examples to show how clever they are, which completely misses the point. You nail it every time. Cheers Kyle.

[@theretroman3862]

Freakin' finally! I understand recursive functions! Not only that, but now I am starting to see how algorithms play a role in making the life easier! Thank you so much man! \m/

[@mohammedalmukhtar8949]

Thanks for this video, Kyle! I used it to create a factorial function function printFactorial(n, total=1) { if(n

[@WebDevSimplified]

Nice job! I love to see people taking my videos and expanding on them.

[@angelcaru]

I have a simpler implementation: function printFactorial(n){ function factorial(x){ if(x === 0) return 1; return x * factorial(x-1); } console.log(factorial(n)); }

[@CAPS_AMERICA]

I wished I should have seen this before I took my technical exam! I was using iterative approach all the time (for, forEach) and I didn't have the recursive mindset! You are so awesome man! The detailed way of how you teach, and how you look after your hair! Just great! Go Selsun Blue!!!!!

[@FlightNSurf]

Wow. After years of CS. I finally understand recursion dude. Thank you dude!

[@SnowblindHallur]

Recently bumped into your channel and just have to say you deserve mad props. Your videos are so simply explained and straight to the point. Keep it up!

[@WebDevSimplified]

Thank you so much!

[@keerthans2366]

Learning Recursion was impossible until I watched your video sir. This video also helped me to revise complex array and arrow function.

[@jadekinstudio]

Thanks! I was really rusty in recursion and now makes sense again!

[@MietekPomywacz]

This is actually an awesome video, I gotta say I tried doing everything myself as soon as he explained it clearly at the start that its pretty much similar to a loop but differs with the fact that you choose when to escape it with a condition and I managed to do all of these examples before he has shown a solution. Again, AMAZING VIDEO!

[@FromTheHeart-777]

You are a blessing to me. Just want you to know. You get straight to the point and use realistic examples. I have passed your channel to fellow students in my bootstrap. Thanks for everything.

[@faisalhossain151]

omg the second example was a very nice practical application of recursion. most recursion examples i see on the internet are like fib sequences and factorial, which is alright, but i really wanted to know a practical use of recurison, thank you for the video as always :)) edit: I meant the third example woops

[@WebDevSimplified]

You're welcome. I try to include practical examples when possible because it helps solidify why something should be used, because it is hard to know when to use something if you never see it used.

[@nachomarquez7541]

Change the title of the video to "Recursion made damned easy". Thanks a million sir!!

[@Quidoute]

Recursive functions are really useful I use them almost everywhere because it gives more controle of what's going to happen by passing different arguments

[@RamadhaniShemahonge]

This is the simplest explanation ever.. May God Bless you

[@chandlerliu3010]

I like this kid a lot!!! --> Very succinct and explanatory (hundred times better than other programmer vloggers on youtube)

[@3491da]

By far the best explanation for recursion Ive come across, well done and thank you

[@nizamuddinshaikh3185]

Vow, so tough a topic, so simple an explanation! Wonderful tutorial! Thank you Kyle. 👍😃

[@micoberss5579]

My version of sumRange: function sumRange(n){ ... if(n

[@WebDevSimplified]

Nice job!

[@how_to_bim6341]

in this case better than the original ;)

[@Tijme]

My version of sumRange: function sumRange(n) { return n === 1 ? 1 : sumRange(n-1)+n; }

[@MrChrisJ74]

Man the web needs more ppl like you. Very good communicator, I am gonna subscribe to one of your courses based on this one lesson

[@ndbass09]

I know this wasn't the point of the video, but I really appreciated the use-case scenario of a family tree with the tree model. It helped make using that data structure click for me.

[@p2lifau]

bro is really the goat. immaculate patience

[@armandobueno1681]

Videos like this make competitive programming a lot easier

[@chrisoleary8401]

Thanks for this video. Where I'm still confused though is in trying to understand how the variable 'child' works in this recursive function. I don't see 'child' defined as a variable within the tree, so how does the function recognise it? How does the function pull the name values (e.g. 'John', 'Jim' etc) from **child.name** when in the tree, these are the values of the *children* property, not child? I'm also still struggling to understand how recursive functions "go back up through the loop" (i.e. where you show it returning in reverse order at 4:52). That just doesn't make sense to me at this point. I don't think it's overly important because I at least understand how a recursive function behaves now. But understanding why it does this still isn't clear.

[@robhills1]

A bit late in the day, so may help someone else, first suggestion is understanding JavaScript ES6 - essentially what is happening is "child" is the variable name given to the results of "t.children.forEach", another way to look at it is if the JSON file was obtained using the "fetch" api you could do something like this (note that there are no variables called "res" or "data" beforehand, these are part of the ".then" methods and declared within them - so firstly create the JSON file (call it "children.json"): { "name": "Bert", "children": [ { "name": "Jim", "children": [] }, { "name": "Zoe", "children": [ { "name": "Kyle", "children": [] }, { "name": "Sophia", "children": [] } ] } ] } In your "script.js" comment out the "const tree = ....." and add: let tree = fetch('children.json') .then(res => res.json()) .then(data => tree = data) Run the application as normal - hope this helps and explained somewhat properly - someone with more experience could definitely improve on this, but my rudimentary understanding anyhow :).

[@erikalonso5782]

@@robhills1 Thank you! I'm still struggling to understand this, but now I know exactly where to look at. Thank you! I though it was a JS property...

[@rahalmehdiabdelaziz8121]

this video was part of my Bootcamp learning journey and it's very helpful 👍

[@cannabisanomaly]

mind if i ask how it went with the bootcamp? were you able to find a job after it?

[@rahalmehdiabdelaziz8121]

@@cannabisanomaly tIt's very helpful especially for people that have good basics in dev, after finishing the front end part of the bootcamp (before finishing the backend part ) I published my resume and my angellist profile in linkedin (which was a task of the bootcamp) and then I get contacted by on of my previous university colleages that launched a startup and got a front end job,

[@cannabisanomaly]

that's awesome, congratulations! i know some people who go 6+ months without finding a job in the current market. good job my internet pal

[@acanthoscurriageniculata7141]

This video is really helpful if you pay attention. To anyone who doesn't understand some part of it, try to focus more on call stack

[@andrewlee7574]

Before watching this, I am not sure why we would use recursive function when normal loops can do the job. Thanks for another quality and short video!

[@CAPS_AMERICA]

WE CAN USE RECURSIVE FUNCTION TO READ ROWS FROM THE DATABASE, DELETE THEM ONE BY ONE, THEN INSERT THEM ONE BY ONE, THIS IS IN PRODUCTION ENVIRONMENT

[@aghileslounis]

Give this man a medal !

[@canklc5772]

Best video on recursive functions

[@stith_pragya]

Thank You So Much for this wonderful video............🙏🏻🙏🏻🙏🏻🙏🏻🙏🏻🙏🏻

[@justhorse3584]

You are the best teacher mate, i mean it. Thank you so much!!!

[@HillelGarciaAustria]

Very nice stuff! You explained it very good. Thank you. Just once thing, in the sumRange function, you don't need the total param. It gets accumulated with the same function recursion, like so: const sumRange = n => (!n) ? 0 : n + sumRange(n-1);

[@fithamlakfikrie4657]

great explanation, specially the third example gives a sense to use recursive function, Thank you 🙏

[@MachiriReviews]

Great video, these things were daunting at first but all the knowledge from others really puts it into a simpler perspective

[@rimantasdanilevicius6754]

good example. I felt like i need one more a little bit complicated example to get though the logic! Your way of explaining is really good.

[@karthikkumaresan1091]

Its 11:30 in the night and watching this video is the best thing that I did all day!! :).. Thanks!!

[@absolustely.honest82]

Almost all recursive functions can be substituted by a for loop. So this is more of a nice to have than an absolute necessity. Great tutorial BTW.

[@milkybrmaji7192]

Best and easiest explanation

[@kirtanthakkar813]

Such an amazing way to explain recursion! This is exactly what I wanted! 🙌 Thank you! :)

[@RandomNekato]

Thank you very much for the comprehensive explanation. Your videos are a blessing

[@depressito]

thank you for making these video that make my life so much easier

[@JT-iw2cw]

4:30 I thought functions resolved the moment it hits any return statement. I don't understand what it's doing stepping out of the if() statement, returning multiple times. I think it would only bubble up if the if() statement were within it's own function, unless the interpreter sees the if statement as it's own function, which I didn't think was the case. -edit: I understand now, you're not referring to the same function running, but a new instance each time the inner call is made.

[@DanThemes]

Same at 8:30, I still don't get what he's saying. The moment the if condition is true, it returns a value (not the same recursive function again) so that return statement exits the function.

[@michaelx3553]

This makes so much sense... I love wds the more after every video

[@tiagolelinskimarin4242]

I thin it doesn't get any clearer than that! I would just add some more console.logs there in some places to illustrate a little further some functions. But the way he explains is just amazing!

[@adrianojedaf]

I got a bit lost with the last example. I will come back to check on that again later. Excellent explanation.

[@iyobosajefferson6457]

This is great! Never seen such a video wonderfully explaining recursion!

[@matthewblasco4720]

omg thank you for this!!! I literally needed this because I solved the tree problem using multiple maps XD didnt know recursive is a thing and a few line of codes only

[@Alexjay1234]

Thank you for explaining how that works in psuedo code. That really helped me.

[@HaRmonikBeats]

This was an great explanation best I’ve seen on KZbin great for beginners to learn from 💯🔥

[@martinacosta9972]

When im confused, and see you have a video on the topic, i know soon i wont be confused

[@lukehatcher98]

You are an excellent teacher

[@james.kaloki]

Dude thanks a lot I was seriously struggling to learn this concept in school

[@edyta9877]

Thank you for all your work with this channel! It helps me a lot!

[@tommy10436]

Thanks, dad. at 4:27, when you say you move back up into countDownRecursive(1)... Why does it move back up in 1, 2 and 3, and not just exit out of the function?

[@leonardoragazini]

exact same doubt I have

[@davekaushik4863]

Thank you so much for this video, recursion makes a lot more sense thanks to you!

[@Self-taughtCoder]

Wow, thanks for the video. Really helpful. I also did it like this. I hope it's ok! function sumRange(n) { if (n

[@chisomodimmegwa3479]

dats the way, seems he was overthinking it

[@mikeba3809]

You should change your article about recursion so that the coding examples match up. I found the coding examples you used in this video to be more familiar and hence, more relatable, than the ones you used in your article.

[@p86167]

Such a good example and made things super easy

[@osvaldodiasdossantos6625]

Not an easy topic to explain, it seems, but you did it. Thanks.

[@NITESHSINGHNRS]

best teaching technique.....

[@randerins]

Perfect! You made it very simple to understand

[@coreyheckler7891]

These videos are fantastic. Keep up the hard work dude!

[@WebDevSimplified]

Thanks!

[@6848811]

Great Explanation. Great Examples. And tells you why it is needed. Good job 👍🏻

[@greenie62]

A benefitting 13 minutes that was. Well done. 👍

[@brecoldyls]

I like how you used tail recursion in the second example. I think it’s clever how you used default arguments to avoid having to make an auxiliary function, I never thought of doing that before 😮

[@hungpewnoy2081]

this problem is so complicated to me and you has just solve my trouble in 13' . so worthy video,thank you.!!

[@joedunder4439]

Another excellent video and another perfect hair day.

[@mikemaer]

You are a great teacher, thanks my dude!

[@Raj-ur7lg]

Very good explanation...thank you Bro for your time!

[@jitu757]

All your video are to the point and easy to pick up and understand. However, the last example is proving to be very difficult. Why did we need to use the foreach id recursion suppose to handle the loop?

[@18.michaelmaramag89]

Awesomeness! Now i understand recursion..

[@1flybyguy]

Really needed the tree recursion example! Thanks!

[@asadurrahman1681]

your channel saving my life

[@good-luck-ugo]

4:25 why do we move up. Shouldn't execution end at the last function?

[@netstormuk]

6:30 return (n < 1) ? n : n + sumRangeRecursion(n - 1);

[@nnokki]

omg you're so beautiful and your voice is so deep😍😍 i was here to learn something but got heavily distracted!

[@ec4150-k4f]

Great vid, can protect that last function against undefined and null values in the objects by adding something like const children = t.children | | [ ]; then using that array instead of t.children throughout

[@marlon4008]

Thank you for sharing these videos. they are so helpful.

[@PatrikRasch]

Nice explanation as always 🙌

[@swadhikarc7858]

so precisely done. though I don't know JS, i could understand each line of code

[@WebDevSimplified]

Thank you. I was really hoping that the code was easy enough to understand even with no javascript knowledge.

[@redlobsta1]

@4:51 - why are there three extra returns in the logic? doesn't the function just return once and its over? whats with the counting up?

[@brydn590]

Yup that part made me even more confused lol

[@certifiedmicronaut4901]

Thank you so much, Kyle!

[@ervinselimovic4888]

Wonderfully explained, thanks!

[@bulentgercek]

I want to make a correction on a very important detail, taking my place. Kyle said at 09:03 it returns 6 for every recursive call. Actually recursive doesn't return over and over. Because the function is called again without closing the scope, it accumulates in the call stack. Finally, after the return in the if, the last called function's scope reaches its end. Then, functions that cannot be closed once in the call stack reach the end of scope one by one. Also, Kyle said at 12:01, 2 more return called for Zoe and John. Actually, this is not true either. Because it only returns for those who do not have children. For others, only the scopes waiting on the Call Stack are closed. To experience this situation, it is enough to Debug in VS Code. You can follow the situation I described from the Call Stack window.

[@case_2]

👍

[@Sandeep-zu7gd]

1) They do return over and over. That is what the return statement is there for. If the inner functions don't return value, there is no way for the outer functions to get the value since it is stored in a variable local to the inner function. 2) Every function in JS returns to the place where it was called (the control flow is returned to the place where the function was called) on reaching return statement or on reaching the end of the function(The JS engine automatically returns with return value of undefined for you if there is no explicit return statement). So, in the case of princtChildrenRecursive(), even though an explicit return statement is only placed when the object doesn't have any children, every inner function returns to the outer calling function on reaching the end of the inner function.

[@nasirkhan600]

I can see you going a long way from her. Awesome content, explained brilliantly.

[@WebDevSimplified]

Thank you!

[@ssimona7317]

Super easy to follow!

[@baggyBr33ks]

am i being daft or am i just not getting why im running back to sumRangeRecursive at 8:26 ? i understood recursion exiting out of the loop when the clause guard condition is met.. i.e. n is now equal to or less than 0 so lets return the total = 6, and then exit the loop altogether. Can someone explain this for me please

[@dawnofhopee]

Thank you very much for the amazing explanation!!

[@VuongPianoSolo]

When I'am watching this video of your's, I hoped that I have a video like this when I study in University.

[@troytian9041]

It's not really common to use, but it's very good to know. Thanks.

[@rodwinpieterse1950]

Recursion making me want to long-jump back into tutorial hell.

[@markramos3203]

HI, I just want to ask how does the recursive function know that it should return 6? since in an ordinary function it should be someFunction() { return 6; }

[@austinwilliams3418]

question, when he does forEach(=> child .. how does it know what 'child' is if theres no variable or property named just 'child'?

[@jurikonradi8941]

It worth mentioning that sumRange(n) =( n *(n+1))/2. It's out of the scope of this great lesson, but just blew my mind when I read about it.

[@ninesquared81]

A good way to visualise that is to list out the numbers in forward and then reverse order. So, let's say we want to add all the numbers from 1 to n. We'll call the result of the summation S. So, S = 1 + 2 + 3 + ... + n. But addition is commutative, so we could also write S = n + (n-1) + (n-2) + ... + 1. We can combine these to get S = 1 + 2 + 3 + ... + n + S = n + (n-1) + (n-2) + ... + 1 ------------------------------------------------------------------- 2S = [1+n] + [2+(n-1)] + [3+(n-2)] + ... + [n+1] 2S = (n+1) + (n+1) + (n+1) + ... + (n+1) There are a total of n 'n+1's, so 2S = n(n+1) S = n(n+1)/2. The anecdote goes that a young Carl Gauss and his classmates were tasked with adding the numbers from 1 to 100 by their teacher. It was meant to take them a while, but Gauss discovered this 'shortcut' and finished very quickly.

[@erikalonso5782]

@@ninesquared81 Thank you for your comment, tying it to a historical event just makes it much more interesting. Take my upvote as I don't have anything else to offer!

[@ninesquared81]

@@erikalonso5782 Thanks. I'm happy my comment was useful! :)

[@saliyapathirana3152]

Great Explanation !!!!