iter-fns is a set of iteration utilities that allow you to construct chains of lazy operations.

iter-fns additionally extends iterables in various opt-in ways, such as reverse iteration (via {@link ReverseIterable}) and sized iterables (via {@link SizedIterable}) where supported.

This allows certain operations to be more efficient when possible, but still abstracts over the underlying container, whether it's an array, a string, or otherwise.

iter-fns additionally guarantees that:

• For functions that return iterables, results are computed lazily with minimal auxiliary space.
• Reverse iteration, when supported, has the same asymptotic runtime cost as forward iteration.
• Iterables are compatible with built in functions that expect iterables, such as Array.from.
• Any function that does any kind of ordering will make use of {@link Compare}.
• Any function that needs any kind of randomness will make use of {@link Random}.

If you need built in JavaScript types to support reverse iteration and sized iterables, you can import {@link shims}.