Function filter

filter<O extends Optional.Base>(
optional: O,
predicate: (value: Unwrap<O>) => boolean,
): Optional<Unwrap<O>>
Filters an Optional based on a predicate. If the Optional is Some and the predicate returns true, returns the original Optional. Otherwise returns None.
Type Parameters
- O extends Optional.Base
  The input Optional.Base type.
Parameters
- optional: O
  The Optional to filter.
- predicate: (value: Unwrap<O>) => boolean
  The predicate function.
Returns Optional<Unwrap<O>>
The filtered Optional.
Example
```
const even = Optional.filter(Optional.some(4), (value) => value % 2 === 0);
const odd = Optional.filter(Optional.some(3), (value) => value % 2 === 0);

assert.deepStrictEqual(even, Optional.some(4));
assert.deepStrictEqual(odd, Optional.none);

const filterEven = Optional.filter((value: number) => value % 2 === 0);

assert.deepStrictEqual(filterEven(Optional.some(6)), Optional.some(6));
assert.deepStrictEqual(filterEven(Optional.some(5)), Optional.none);
```
- Defined in src/functional/optional.mts:533

filter<S>(
predicate: (value: S) => boolean,
): (optional: Optional<S>) => Optional<S>

Filters an Optional based on a predicate. If the Optional is Some and the predicate returns true, returns the original Optional. Otherwise returns None.

Type Parameters

Parameters

predicate: (value: S) => boolean
The predicate function.

Returns (optional: Optional<S>) => Optional<S>

The filtered Optional.

Example

const even = Optional.filter(Optional.some(4), (value) => value % 2 === 0);
const odd = Optional.filter(Optional.some(3), (value) => value % 2 === 0);

assert.deepStrictEqual(even, Optional.some(4));
assert.deepStrictEqual(odd, Optional.none);

const filterEven = Optional.filter((value: number) => value % 2 === 0);

assert.deepStrictEqual(filterEven(Optional.some(6)), Optional.some(6));
assert.deepStrictEqual(filterEven(Optional.some(5)), Optional.none);

Function filter

Type Parameters

Parameters

Returns Optional<Unwrap<O>>

Example

Type Parameters

Parameters

Returns (optional: Optional<S>) => Optional<S>

Example

Settings