@studnicky/v8/array-from-map-callback

Array.from(iterable, mapFn) pays real iterator-protocol and per-element call overhead. Measured on Node v24 (2,000,000 iterations, JIT-warmed), a manual new Array(n) plus an index-assignment fill loop runs roughly 58x faster than the two-argument Array.from form for the same output. Prefer manual index-fill, or drop the map argument and use single-argument Array.from(iterable).

Fixable: No · Options: No · Suggested severity: error

✗ Incorrect

const a = Array.from({ length: n }, (_, i) => i * 2);

✓ Correct

const a = new Array(n);
for (let i = 0; i < n; i++) { a[i] = i * 2; }

const a = Array.from(iterable);