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filter_async

Note

This is a point-in-time snapshot of the API documentation from January 2026. Going forward, we will not be maintaining a public copy of these references, and recommend users to refer to the built-in signature helpers available in the Hack LSP instead for complete and up-to-date information.

Returns a new dict containing only the values for which the given async predicate returns true

namespace HH\Lib\Dict;

function filter_async<Tk as arraykey, Tv>(
  KeyedContainer<Tk, Tv> $traversable,
  (function(Tv): Awaitable<bool>) $value_predicate,
): Awaitable<dict<Tk, Tv>>;

For non-async predicates, see Dict\filter().

Time complexity: O(n * p), where p is the complexity of the synchronous portions of $value_predicate Space complexity: O(n)

The IO operations for each of the calls to $value_predicate will happen in parallel.

Parameters​

Returns​