Don’t pay the for-loop tax

https://dev.to/danhomola/dont-pay-the-for-looptax

by bhalp1 • 9 years ago

11 6 9 years ago

dev.to

kennethkl• 9 years ago

why are all the solutions to for-loop, a different kind of for-loop? aren't you still paying the tax?

joezydeco• 9 years ago

Right. Show me the compiled object code and tell me how much faster it is.

"Debugging is twice as hard as writing the code in the first place. Therefore, if you write the code as cleverly as possible, you are, by definition, not smart enough to debug it."

— Brian W. Kernighan and P. J. Plauger in The Elements of Programming Style.

hdhzy2• 9 years ago

Well if you're comparing for loop to reduce or map in JavaScript then for will always win as it is a built in language construct and reduce involves costly callbacks. Interesting that the difference is only 7% on my Chrome for Android [0].

[0] https://jsperf.com/foreach-vs-reduce-vs-for-loop

For loops have also an advantage that they can be used with yield and await (generators and async functions) while you cannot place these keywords inside a callback function.

hibbelig• 9 years ago

The tax the OP is talking about is not the iteration itself, it's the book-keeping required by the form of the `for` loop.

One example: if you want to iterate over the elements of an array `a` of size `n`, the header of the `for` loop will look like this:

    for (i=0; i<n; i++) {
        element = a[i];
        ...
    }

The `i=0` part is related to knowledge that the first element of an array has index zero, and the `i<n` part kind of follows from it -- if `n` is the length of the array, and `0` is the first index, then `n-1` is the last index.

Compare this to

    a.forEach(function (element) { ... })

Here, you don't have to know that the first index is 0 and you can't make the mistake of writing `<=` where `<` would have been correct.

So the "tax" that the OP is talking about is the cognitive overhead of having to know all these things about the array representation, and making sure to get these details right.

Don’t pay the for-loop tax

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