filter

array →
filter(
    predicate: predicate
) → array

Applies a predicate expression to each input item and returns only items for which the predicate evaluates to true. Returns null when the input is not an enumerable or is a string.

Parameters

Name	Type	Required	Description
predicate	predicate	Yes	Expression defining the predicate applied to each input item.

Argument evaluation

Visits each element of the array or each pair of the dictionary supplied as pipeline input to this filter call, in enumeration order.

• predicate: Evaluated once per visited element, with that element as its context. For dictionary input, $key and $value resolve to the key and value of the visited pair.

Behavior

Argument form — predicate: A predicate call, such as greater-than(1), or an open expression that produces a Boolean, such as .active. A bare Boolean literal such as #true is not accepted.

Element binding: The predicate runs once for each element of the array supplied as pipeline input to this filter call. At the start of the predicate, .field reads that element’s field. In .lines | filter(.active), the inner predicate receives a line from the .lines array, not the surrounding record.

Dictionary traversal: A dictionary supplies its pairs directly, in dictionary order. The predicate receives each pair as its context; $key and $value access that pair. The result is an ordinary array of unchanged selected pairs. An empty dictionary produces an empty array.

Examples

{1, 2, 3} | filter(greater-than(1)) → {2, 3}
{{active:=#true}, {active:=#false}} | filter(.active) → {{active:=#true}}
!{"BE" => 100, "FR" => 80} | filter($value | greater-than(90)) → {("BE" => 100)}

Kind: Function
Scope: array
Aliases: filter