@studnicky/v8/array-from-iterators

Disallows a narrow manual iterable drain: a fresh empty array declared immediately before a for...of loop whose sole body statement pushes that loop binding. It applies only when type services prove the iterable is not an array or tuple; without that proof it reports nothing. Accumulating into an existing or non-empty array and copying or filtering an array remain outside its scope.

For a 5,000,000-entry Set in Node v24, Array.from(set) takes 5.64 ms and [...set] takes 5.57 ms, a 0.99× performance-neutral difference. A for...of plus push takes 42.50 ms, 7.53× slower, while preallocation plus index filling takes 30.01 ms, 5.32× slower — Array.from/spread over a built-in Set/Map hit an internal fast path that a for...of loop's iterator-protocol calls do not, so a manual loop is the slowest option measured. Use Array.from(iterable) or [...iterable] instead. Array.from(iterable, mapFn), the two-argument mapped form, is a distinct concern covered by array-from-map-callback.

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

✗ Incorrect

const values: number[] = [];
for (const value of sourceSet) {
  values.push(value);
}

const entries: readonly [string, number][] = [];
for (const entry of sourceMap) {
  entries.push(entry);
}

✓ Correct

const values = Array.from(sourceSet);

const entries = [...sourceMap];