Time complexity of Array.from

问题

What would be the time complexity of Array.from(). For example:

const set = new Set();
set.add('car');
set.add('cat');
set.add('dog');

console.log(Array.from(set)); // time complexity of making this convertion from Set to Array

回答1:

It's O(n). When used on an iterable (like a Set), Array.from iterates over the iterable and puts every item returned into the new array, so there's an operation for every item returned by the iterable.

回答2:

It is always going to be O(n) as the number of iterations would be directly proportional to the number of elements in the set. Actual Time complexity would be O(n) for retrieving values from a set O(n) for pushing into an array.

O(n) + O(n) = O(2n)

But since we do not consider a constant value when calculating using n value it should be O(n).

来源：https://stackoverflow.com/questions/59172980/time-complexity-of-array-from