1 line of code: How to get every even item of an Array
source link: https://dev.to/martinkr/1-line-of-code-how-to-get-every-even-item-of-an-array-3pl3
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Posted on Nov 10
1 line of code: How to get every even item of an Array
One line of code (JS) (16 Part Series)
const evenItems = (arr, out = [], i) => { for (i = 0; i < arr.length; i = i + 2) out.push(arr[i]); return out; };
Returns an array which contains every even item of the original array.
The repository & npm package
You can find the all the utility functions from this series at github.com/martinkr/onelinecode
The library is also published to npm as @onelinecode for your convenience.
The code and the npm package will be updated every time I publish a new article.
Happy coding and consider to buy me a coffee
Photo by zoo_monkey on Unsplash
Discussion (7)
Or you use the fastest possible version:
const evenItems = (arr, out = [], i) => { for (i = 0; i < arr.length; i = i + 2) out.push(arr[i]); return out; };
I mean, you could just use a filter, which is faster and from my point of view is also more readable:
const evenItems = array => array.filter((_, index) => index % 2 === 0);
Cheers!
Hi Luke,
you are right filter is more intuitive, but it is actually slower for me.
Cheers!
thank you for taking the time to contribute, I put both functions to the performance benchmark on hasty and I'm going to update the article with your suggestion!
Cheers!
You forgot to run the code in that benchmark, so you're only testing the declaration of both functions, not the actual function running ... here you have an actual comparison. With filter it is faster.
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Hi Luke,
yes you are right :D Here is the updated benchmark on hasty - filter is much slower for me.
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Try moving the funciton declarations to the global block (you only need to declare them once and then run them). Maybe is slower in non-chromium browsers, I'm testing on Chrome.
Edit: Tried it in Safari and performance sucks there. Chromium makes optimizations in this kind of algorithms that other browsers don't. From a logic stand point the for approach effectively should run in half the time because is skipping the odd indexes instead of filtering them. Still I would prefer that other browsers optimize my code as Chromium does so I can write simple code and it gets optimized for me.
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