CodeNewbie Community 🌱

Discussion on: Another way to understand JavaScript's array.reduce

View post

Replies for: Hey thanks Robert! That's a totally fair question. I've def seen nested reduce loops before, but it can be difficult to read if you throw everythin...

Collapse
 
r002 profile image
Robert Lin • • Edited

Very cool, thanks for sharing, Ben! I never knew about array.flat until today. Very neat. 👍

Everyday, I seem to find a new use for array.reduce though. It's seriously the gift that just keeps giving! 😄 Just this morning, I was searching for an equivalent to Python's counter data structure in JS and found this:

var arr = [5, 5, 5, 2, 2, 2, 2, 2, 9, 4]

const map = arr.reduce((acc, e) => acc.set(e, (acc.get(e) || 0) + 1), new Map())

console.info([...map.keys()])
console.info([...map.values()])
console.info([...map.entries()])
Enter fullscreen mode Exit fullscreen mode

What a beauty! What a time to be alive!! 🚀

Source: stackoverflow.com/a/57028486

Thread Thread
 
bholmesdev profile image
Ben Holmes •

Haha yeah, love the enthusiasm 😁

Agreed, reduce is for a lot more than just reduce-ing arrays to something smaller (like a number of a string). That's why some languages like Rust and Kotlin call it "fold." That's because you're "folding" something of one data type (like an array) into something of another data type (like a Map in your example). Doesn't mean we've reduced it, we've just changed it into something different!