Trying to see the most efficient way to flatten an array of n-nested arrays within it. I've just been using flat() for one-level nested arrays but is there a time-efficient helper function I can add to my app to universally flatten all arrays, regardless of n-number of nested arrays?
1 Answer
You can use either recursive algorithm or use stack:
function flatDeep(arr, d = 1) {
return d > 0 ? arr.reduce((acc, val) => acc.concat(Array.isArray(val) ? flatDeep(val, d - 1) : val), [])
: arr.slice();
};
function flatten(input) {
const stack = [...input];
const res = [];
while(stack.length) {
// pop value from stack
const next = stack.pop();
if(Array.isArray(next)) {
// push back array items, won't modify the original input
stack.push(...next);
} else {
res.push(next);
}
}
// reverse to restore input order
return res.reverse();
}
Using generator:
function* flatten(array, depth) {
if(depth === undefined) {
depth = 1;
}
for(const item of array) {
if(Array.isArray(item) && depth > 0) {
yield* flatten(item, depth - 1);
} else {
yield item;
}
}
}
Source: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/flat
2 Comments
Pauline Nemchak
should I delete my answer? I can't leave comments yet
blex
Well, that's a correct answer, and you cite the source, so you're fine. Oh, and you can now comment 🎉
Array.flat(), you'll see the code to do just that. They call itflatDeep