Getting the square with reduce()

[colinthornton]

But reiterating what the other guys said above, filter and map would be far easier to understand in this situation.

reduce, while powerful, is seldom legible outside of a few common operations like summing an array of numbers.

[kevinSmith]

Yeah, reduce to me is semantically correct when you are reducing to a single value, like summing. In general, I prefer to use the method whose implication is closest to what I am doing. Here, we are mapping and filtering. Someone could argue that doing it in two steps is a little less efficient (O(2n) instead of O(n)), but it is highly unlikely to make a real difference and the loss in readability outweighs the imperceptible (if that) gain in performance.

[NKos]

I was able to understand how to solve this problem with map and filter but reduce function still confuses me a little bit. I can follow what is being done when I read a reduce function but when it comes to writing one on my own, I find it challenging. Hope this is normal for newbies.

[kevinSmith]

@NKos

Hope this is normal for newbies.

Very. Of all the Array methods, it is the one that causes the most confusion. I once had to explain how it works to a senior dev - seriously.

My suggestions for learning the prototype methods is to write your own functions. Write your own “myMap” function that accepts the array and the callback and uses a loop to do what the map method does. Then do it for filter and find. Then see if you can make a reduce. Then (if you want) see if you can build the other methods using just reduce.

Or just spend some time with reduce. I’m sure there are a lot of youtube videos out there - watch 10 of them. Then build some code. reduce is a weird one until you get the hang of it, then it is obvious and easy. But yeah, until it “clicks”, it just seems really weird.

[iamsobahan]

If you want to use reduce method ,then you have to mention extra parameter for initial value and must mention your desired value like array.reduce(callback function,initial value)