Map

:::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 function on the original value

namespace HH\Lib\Vec;

function map<Tv1, Tv2>(
  Traversable<Tv1> $traversable,
  (function(Tv1): Tv2) $value_func,
): vec<Tv2>;

For async functions, see Vec\map_async().

Time complexity: O(n) Space complexity: O(n)

Parameters

• Traversable<Tv1>$traversable
• (function(Tv1): Tv2) $value_func

Returns

• vec<Tv2>

Examples

$numbers = vec[1, 2, 3];
$new_numbers = Vec\map($numbers, $number ==> ($number + 1));
echo "new numbers are: \n";
\print_r($new_numbers);
//Output: new numbers are: 
//vec[2, 3, 4]