🧩 Yields each item the first time it is seen.
Syntax
TypeScript
import { uniqueIter } from '@opentf/std'; uniqueIter<T>(iterable: Iterable<T>, by?: (val: T) => unknown): Generator<T>
Parameters
iterable: The source iterable.by(Optional): The iteratee invoked per item to derive its key.
Returns
A new generator without duplicates, in first-seen order.
Items come through as they are read, so an early duplicate-free prefix is available before the source ends — but the keys seen so far are held, and that set only grows. On an unbounded source of distinct values it grows without limit, as any deduplication must.
Primitive keys are matched by identity, so NaN equals NaN and -0 equals 0. Object keys are compared structurally with isEql, matching unique, and against every distinct object seen so far — quadratic in the number of them, so prefer a by that returns a primitive when the source is long.
Examples
TypeScript
[...uniqueIter([1, 2, 2, 3, 1])] //=> [1, 2, 3] const users = [{ id: 1 }, { id: 2 }, { id: 1 }]; [...uniqueIter(users, (u) => u.id)] //=> [{ id: 1 }, { id: 2 }]