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Map Async

hphp/hack/manual/hsl/Functions/HH.Lib.Vec/map_async.md

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:::info[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 vec where each value is the result of calling the given async function on the original value

Hack
namespace HH\Lib\Vec;

function map_async<Tv1, Tv2>(
  Traversable<Tv1> $traversable,
  (function(Tv1): Awaitable<Tv2>) $async_func,
): Awaitable<vec<Tv2>>;

For non-async functions, see Vec\map().

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

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

Parameters

Returns

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