Another good reason to set the second parameter on the reduce is if you are totaling price on an object (like in your example) and you didn't set this parameter to 0, then total would represent the object (the first item in the array) and your code would error out. Thank you for this video Kyle.
Last week I was struggling with aggregate of object attributes in an array of objects due to the missing intiial value of 0 and I learned it the hard way. Also I had the groupby use case well. Thanks for simplying groupBy.
best explanation of reduce in javascript that i have ever seen. be cautious saying amunnuh when you mean “I’m going to”. that can be difficult for non native listeners
I think you said the best definition of reduce ever. "Reduce, all it does. It takes array of values whatever that is and reduces it down to one single value"
very good explanation of the reduce method, it is clear and simple. I'm a french developper in training and I understood everything, thank you and good continuation for your TH-cam channel
While I understood how reduce worked, I didn't quite get why I kept hearing how powerful it was - your object example made it very clear in a short amount of time!
This guy really uploaded this video 2 weeks ago and today I needed to use reduce and didn't know it worked, now i do thanks man. Whenever I need to understand something new I just type the concept + webdevsimplified and watch ur video lol
Dude... you're amazing! Thanks a lot! You're so much better than my teacher LOL Thanks for your content! I'll be buying your course soon. :) Have a nice day!
I like the reduce function. But many people use it on occasions where a simple `forEach` loop would be more appropriate, and that gives the `reduce` a bad reputation, because it seems to make things unnecessarily complicated. I think you should always be aware of that whenever you are about to use it.
6:57 Took me a while to make this work; you can write this as const toArray = (arr, elem) => arr ? [...arr, elem] : [elem] const grouper = (grouped, { age, name }) => ({...grouped, [age]: toArray(grouped[age], name)}) console.log(people.reduce(grouper, {})) assuming you want a list of names instead of the full objects, as specced at 5:49. At least destructuring the age and name is clear enough; some of the syntax may be a bit obscure.
I love the _reduce_ method. I use it for everything. I would brush my teeth with it if I could. If you ever _map-filter-map-find_ anything, do everyone a solid and just use _reduce._
Good explanation Kyle! I think the second example should use undefined rather than null, then you can use strictly equals like so: if (groupedPeople[age] === undefined) groupedPeople[age] = []
Thanks man! Been hating the tasks which force you to use reduce so far.. feels like you randomly try until it somehow works. I really don't get why this feels so awkward to use or understand but your examples were extremely clear and helpful. Perhaps now I can stop dreading the reduce method. 😅
The reduce method is a double-edged sword, as explained by a Google Developers video: th-cam.com/video/qaGjS7-qWzg/w-d-xo.html On the one hand, the reduce method is handy On the other hand, it might reduce the readability (see the pun?)
excellent last bit about "make sure to give reduce() a default starting accumulator value, else your code will fail if given an empty array" however: what is the rationale using "==" operator, vs. strict equality "===" ?: that is standard practice in nearly 100% of operational JS code I've worked on
The reason why you receive the array as 4th parameter is because the callback function might be inside another file or might or be outside the scope of the array, so you can't reference it in any way. AFAIK all array methods have a callback function that pass the array as an argument.
Thanks a ton for demonstrating the advanced features as well and the consequence of leaving the default parameter empty. That's not something everyone out here does.
Thank you so much. I saw many videos on YT of reducing the items to a single value (easy one), but NO one explained about the grouping items into categories. This literally save so much processing power. I was using two loops of approx 1000 items and approx 100 items each to categorize. But this reduce method of categorizing is so much efficient. Thanks for explaining the concept :)
The easiest explanation of reduce is that it's a same low level function as "for loop" but in completely functional way. It's safe, returns result, code is declarative and immutable and you can build other functions like filter, map,etc with it.
@@kirillvoloshin2065 “a completely functional way “ that’s nuanced AF. “Safe” noobs don’t know what safe is vs not safe. Not knowing when you’re in danger is kind of the essence of noobness. “Declarative and immutable” by the time you have a good grasp on all those terms you don’t need a video explaining reduce. Back to my point that engineers often forget how to explain things to people several levels below them.
@@proactivex Sorry but from my perspective reduce is not something that you learn in your first 2 weeks of programming. This is why "easy explanation" is not for people who just started. It's for people with background which want to learn reduce. You should for sure understand the difference between imperative and declarative programming as well as functional vs oop approaches.
@Anmol Pandey it's the opposite. reduce is declarative programming and for loop imperative. Imperative programming consists of a series of commands which do something and it focuses on describing each command. Declarative programming consists of expressions and not commands. We describe what needs to be done but not the each step of how it should be done.
how can i delete the data, when using Reduce. for example, if you look at the 6:42 at the video, i wanna delete sally, and jill because they are same age.
Hi, I'm kinda new and I don't get the second example. Why does he do groupedPeople[age]? Why there are square brackets? it is not an array, it's an object but he treats it like an array. I think I'm missing something here...
This was the most simple and straight forward example of reduce I've seen. Thank you!
Another good reason to set the second parameter on the reduce is if you are totaling price on an object (like in your example) and you didn't set this parameter to 0, then total would represent the object (the first item in the array) and your code would error out. Thank you for this video Kyle.
Thank you for this! I just took a whole course about it and got even more confused. Your video broke it down to a point where it clicks.
I've watched this video twice, once before ~5 months and now after forgetting what "reduce" does... and im so thankful every time! Thank you!
Last week I was struggling with aggregate of object attributes in an array of objects due to the missing intiial value of 0 and I learned it the hard way. Also I had the groupby use case well. Thanks for simplying groupBy.
4:12
best explanation of reduce in javascript that i have ever seen. be cautious saying amunnuh when you mean “I’m going to”. that can be difficult for non native listeners
I think you said the best definition of reduce ever. "Reduce, all it does. It takes array of values whatever that is and reduces it down to one single value"
very good explanation of the reduce method, it is clear and simple.
I'm a french developper in training and I understood everything, thank you and good continuation for your TH-cam channel
I cant believe how you made it that simple. Thank you!!
I've been stuck on understanding reduce for 2 days now. This video cleared everything up. Thanks!
best explanation. my scalp is starting to regrow hair follicles thanks to u
10 minutes of this is so much better than 1,000 hours of understanding the docs
While I understood how reduce worked, I didn't quite get why I kept hearing how powerful it was - your object example made it very clear in a short amount of time!
I'm at least watching the ads cause this guy explained reduce briefly and concisely :) and nice hair btw
Man, you helped me solve a problem that's been kicking my butt for a LONG time. THANK YOU!
7 the video on reduce in the last 40 mins and this is as simple as you can get...superb. A like and a subscribe from me.
This guy really uploaded this video 2 weeks ago and today I needed to use reduce and didn't know it worked, now i do thanks man. Whenever I need to understand something new I just type the concept + webdevsimplified and watch ur video lol
Dude... you're amazing! Thanks a lot! You're so much better than my teacher LOL
Thanks for your content! I'll be buying your course soon. :)
Have a nice day!
I like the reduce function. But many people use it on occasions where a simple `forEach` loop would be more appropriate, and that gives the `reduce` a bad reputation, because it seems to make things unnecessarily complicated. I think you should always be aware of that whenever you are about to use it.
LOL - after googling for HOURS(!!!) I finally got it - after just 3min into this video. Damn good explanation! Thank you sooo fkn much!!!
Thank you VERY MUCH! All CLEAR NOW FOR ME and you made video without any extra "bloggers show off". My like to you and subscription.
I'm looking forward for more videos about array, string, and object methods.
Your explanations are so great.
same
after your explanation this is my fav method
best explaination i used for loop each time but now onwards i am shifting to reduce
I have used reduce() many times. but clearly understand now. Thanks Kyle.
you REDUCED my effort of understanding the "reduce" function. 👌
I've watched a fair few videos on reduce, but you have explained this wayyyy better.
I was looking for resources to learn about `reduce` method. Your video came in as a rescue Kyle.. 😍
You are a saviour!!
The concept of reduce method is very well explained because it was difficult to understand the concept of this in the documentation.
Thanks.
Thank you Kyle, I saw .reduce in a TS tutorial, i had no idea how to do it, your video was straightforward
6:57 Took me a while to make this work; you can write this as
const toArray = (arr, elem) => arr ? [...arr, elem] : [elem]
const grouper = (grouped, { age, name }) => ({...grouped, [age]: toArray(grouped[age], name)})
console.log(people.reduce(grouper, {}))
assuming you want a list of names instead of the full objects, as specced at 5:49. At least destructuring the age and name is clear enough; some of the syntax may be a bit obscure.
I love the _reduce_ method. I use it for everything. I would brush my teeth with it if I could. If you ever _map-filter-map-find_ anything, do everyone a solid and just use _reduce._
Good explanation Kyle!
I think the second example should use undefined rather than null, then you can use strictly equals like so:
if (groupedPeople[age] === undefined) groupedPeople[age] = []
you can go even further using `.hasOwnProperty()` to check object key
null and undefined are falsy so if(groupedPeople[age]) is enough
Thank you so much! This is so much clearer than other tutorails using acc, cur….
Thanks Kyle for your simplified explanation with useful example
That's an impressive straight forward explanation!
Really liked the analogy with forEach Loop.
Haha, just what i needed. 😆 I literally just youtube-ed how to use reduce function.
All i gotta say is Thank you mate, you're awesome!
reduce is like different and complex from other array methods,but you made clear that for us thanks
You truly simplify the web. thank you!
Thanks man! Been hating the tasks which force you to use reduce so far.. feels like you randomly try until it somehow works. I really don't get why this feels so awkward to use or understand but your examples were extremely clear and helpful. Perhaps now I can stop dreading the reduce method. 😅
I feel lucky that I was able to intuitively understand reduce for the most part. Except that second parameter. That tripped me up hard quite a bit.
Perfect content coverage on reduce. You are amazing! Thank you for sharing.
Was legit looking for this today and my man ends up making a video on it. Coincidence? I think not
Nice video bro, i finally have understood how to filter objects by a key with reduce thx man .
Shalom Mr. K, outstanding explanation!
Thank you
Shalom
You deserve more subscribers
Very well explained, crystal clear. Thanks for this content!
Thank you Kyle. You are great !
Incredibly well explained! Thanks so much! 🙏
This is amazing, and really helpful. I have immediately subscribed. And I think I love you sir. :)
I appreciate how you show multiple use cases instead of just the most simple one. Keep up the amazing videos!
Thank you, I understand it much better now!
7:12 don't the groupedPeople[age] shows the value present in groupedPeople array at indext position age? So how does it make sense??
Dude your explanations are so good. Thank you!
u are amazing, all ur video is concise and easy to understand
Thanks bro. I'm a JavaScript developer and never understood this function. You truly "simplified" it
Much appreciated! This can definitely be a time saver
Simple and direct, great explanation.
This is just awesome! Finally, I get it.
loved the seccond example , love from india .
The reduce method is a double-edged sword, as explained by a Google Developers video: th-cam.com/video/qaGjS7-qWzg/w-d-xo.html
On the one hand, the reduce method is handy
On the other hand, it might reduce the readability (see the pun?)
I wonder if we should name the object "vague" and the parameter -- "readability":
const x = vague.reduce((overall, readability)=>{ ....}, 0)
finally, today is the day when I succesfully understood this reduce function. Thanks alot
excellent last bit about "make sure to give reduce() a default starting accumulator value, else your code will fail if given an empty array"
however: what is the rationale using "==" operator, vs. strict equality "===" ?: that is standard practice in nearly 100% of operational JS code I've worked on
This video was really helpful and clear. Thank you!
You are awesome, Kyle! Your videos have helped me learn so much about Javascript👍
amazing explanation ! good job
reduce doesn't only apply for total, total from your addition statement. If you change + to -. it will deduct from initial value by each item .
Amazing explanation. Thank you Kyle!!!🙂
Thank you for a great and easy to understand explanation
Thank you so much! It's make so much sense now.
Im always learning from Kyle ! This is an amazing !!!!
Thanks a lot for such a detailed video.
The reason why you receive the array as 4th parameter is because the callback function might be inside another file or might or be outside the scope of the array, so you can't reference it in any way. AFAIK all array methods have a callback function that pass the array as an argument.
that's exactly right
thanks so much for this explanation!!! it really helped
Dude this just saved me. Thanks!
Thanks a ton for demonstrating the advanced features as well and the consequence of leaving the default parameter empty. That's not something everyone out here does.
you are my life saver! Thank you🙏
Thank you so much. I saw many videos on YT of reducing the items to a single value (easy one), but NO one explained about the grouping items into categories. This literally save so much processing power. I was using two loops of approx 1000 items and approx 100 items each to categorize. But this reduce method of categorizing is so much efficient. Thanks for explaining the concept :)
LIKE :)
Thank you for publishing this video.
Really clear and friendly introduction to reduce() method!
Kyle, I love your videos! You are a great teacher and a superb developer!
The easiest explanation of reduce is that it's a same low level function as "for loop" but in completely functional way. It's safe, returns result, code is declarative and immutable and you can build other functions like filter, map,etc with it.
Typical engineer who has lost touch with what an easy explanation is.
@@proactivex well, I find this explanation pretty clear and straight to the point. maybe because I am too 😏
@@kirillvoloshin2065 “a completely functional way “ that’s nuanced AF. “Safe” noobs don’t know what safe is vs not safe. Not knowing when you’re in danger is kind of the essence of noobness. “Declarative and immutable” by the time you have a good grasp on all those terms you don’t need a video explaining reduce. Back to my point that engineers often forget how to explain things to people several levels below them.
@@proactivex Sorry but from my perspective reduce is not something that you learn in your first 2 weeks of programming. This is why "easy explanation" is not for people who just started. It's for people with background which want to learn reduce. You should for sure understand the difference between imperative and declarative programming as well as functional vs oop approaches.
@Anmol Pandey it's the opposite. reduce is declarative programming and for loop imperative.
Imperative programming consists of a series of commands which do something and it focuses on describing each command.
Declarative programming consists of expressions and not commands. We describe what needs to be done but not the each step of how it should be done.
Thank you kyle, got more clarity on Reduce method now❤😊😊👍
Your hair is always on point 🔥
That was pretty cool explanation
how can i delete the data,
when using Reduce.
for example, if you look at the 6:42 at the video,
i wanna delete sally, and jill because they are same age.
thank you so much , you've covered everything 🤩
Thank you very muh for really breaking this topi. you are the best
Please make more of these byte sized vides (pun intended) just like Kevin Powell does for CSS
This is a perfect explanation, thank you!
Thanks, I never set seccond parameter but from now I will alway set it 😍🥰
I mean that zero
Thanks kyle! Can't get more simple than this
Time worthy video 😍
Hi, I'm kinda new and I don't get the second example. Why does he do groupedPeople[age]? Why there are square brackets? it is not an array, it's an object but he treats it like an array. I think I'm missing something here...
As always a great lecture. Thanks a lot
Good explanation
Keep posting 💥
this is literally the best reduce video i ever seen :) I love how you make it so easy :)
Can u help me out bro?
Wat happens when groupedpeople[age]
@@allenjr4978 try it
@@AlThePal78 bro I cant understand what happens when we declare groupedpeople[age]
@@allenjr4978 when I get home I will help you im at work
So what is up you still there?
you made it clear, thank you
I am new to JavaScript. Could anyone let me know where is the "key" 26/31/42 coming from at 6:45? Thanks