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filter()

filter<Input, Output>(predicate): OperatorFunction<Input, Input>

Defined in: src/Filter.ts:23

Creates an operator that keeps only the items for which predicate returns true.

The predicate must be synchronous and must be a type predicate (value is Output), so the chain method filter can narrow the item type.

Type Parameters​

Input​

Input

Output​

Output

Parameters​

predicate​

(value) => value is Output

a synchronous type predicate

Returns​

OperatorFunction<Input, Input>

an operator function

Example​

const mixed: (number | string)[] = [1, "a", 2, "b"];
const numbers = await chain(mixed)
    .filter((v): v is number => typeof v === "number")
    .toArray();
// => [1, 2]