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How Long Should a Function Be? (And Why It’s the Wrong Question to Ask)
(adamtornhill.substack.com)
this post was submitted on 29 Apr 2026
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Programming
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@codeinabox
A function should be short enough that you can read and understand it.
Unless you're using a language in which each function declaration has a performance or memory-usage penalty. Not an issue if your language compiles to machine code or WebAssembly, but interpreted languages like JavaScript do have such a penalty. In these cases, you may need to make your functions longer to avoid that penalty.
#programming
this sounds like a pretty bad reason to justify ugly code today
any readability gain will greatly outweight resources in most situations
@eager_eagle
That might have been a reasonable statement 3 years ago, but today there is a global crisis caused by extremely high RAM prices. Optimize your blasted code.
Agreed, optimize it. Where it matters. Reducing the number of functions to save space on the stack when the heap has 99% of the data is nonsense.
@eager_eagle
I'm talking about the *code* wasting memory. In JavaScript each function is a heap object and its source code is another heap object. Even if a JIT compiler inlines them, the original non-inlined functions keep sitting there wasting perfectly good bytes.
and again, you end up sacrificing readability to address what, a fraction of a percent in memory use? If that matters in your program, maybe don't use JS.
@argv_minus_one @codeinabox
This is utter nonsense, except you proof with serious performance measurements that
- the extra function is slower
- this actually matters
@HaraldKi
I am admittedly a bit…emotional about not wasting memory. Growing up on a 486 with 4MB of RAM does that to you, I guess.
The extra function will only be slower if the compiler/interpreter doesn't inline it, which most compilers/interpreters including JavaScript will, so it's mostly just a memory-usage issue. But I have used rather simple interpreters that *don't* inline functions, and one of them even came with a warning that function calls are slow!
@codeinabox
@argv_minus_one @codeinabox
Well, well, with JavaScript I think browser snd bloated web sites, where a good hand crafted extra function is the smallest if our problems.🤣