Loops are easier to read. With functions like reduce you have to solve a puzzle every time to understand what the code is doing (this is also true for functional style of programming in general).
> More specifically, maps can be trivially parallelized; same for folds, but to a lesser degree, if the reducing operation is associative; and for-loops are hard.
In a typical Javascript code reduce operation will not be parallelized. It actually can be slower than a loop because of overhead for creating and calling a function on every iteration.
> when you look at the system as a whole lots of for loops
A code with lot of loops is still more readable than a code with lots of nested reduces.
>Loops are easier to read. With functions like reduce you have to solve a puzzle every time to understand what the code is doing
I think that is a function of familiarity, if you use reduce a lot it will be as easy to read as a loop - perhaps easier because more compact - there is a downside to reading more lines for some people, at some point verbosity becomes its own source of illegibility (although any loop that can easily be turned into a reduce probably won't be excessively verbose anyway)
Of course all that is just on the personal level, you , by using and reading more code with reduce in it will stop finding reduce less easy to understand than loops - but the next programmer without lots of reduce experience will be in your same boat.
I disagree quite strongly, in that this is simply a function of familiarity. Reduce is no more or less readable than for (especially the C style for — imagine trying to work out what the three not-really-arguments represent!)
loops are harder to read. What does it do, map, reduce, send emails to grandma?
In JavaScript, the reduce callback is created once and called repeatedly. For loops are pretty much always the fastest possible way because they use mutable state. They are also a really good way of creating unreadable spaghetti that does things you don't want them to.
I'm not sure what you mean by nested reduces. Chained reduce functions are easy to follow
The point was that in map and reduce it's clear what's being done and what's being returned, especially in a typed language. Ideally you're also in an environment that doesn't allow for side effects, in which case, grandma gets no emails from map or reduce
It is not visible what is returned or what is input im case of chaining. Because return and input parameters are not directly visible and you have to read all previous calls to figure that out.
> More specifically, maps can be trivially parallelized; same for folds, but to a lesser degree, if the reducing operation is associative; and for-loops are hard.
In a typical Javascript code reduce operation will not be parallelized. It actually can be slower than a loop because of overhead for creating and calling a function on every iteration.
> when you look at the system as a whole lots of for loops
A code with lot of loops is still more readable than a code with lots of nested reduces.