True Myth / maybe / unwrapOrElse

Function: unwrapOrElse()

Call Signature

unwrapOrElse<T, U>(orElseFn, maybe): T | U

Safely get the value out of a Maybe by returning the wrapped value if it is Just, or by applying orElseFn if it is Nothing.

This is useful when you need to generate a value (e.g. by using current values in the environment – whether preloaded or by local closure) instead of having a single default value available (as in unwrapOr).

import Maybe from 'true-myth/maybe';

// You can imagine that someOtherValue might be dynamic.
const someOtherValue = 99;
const handleNothing = () => someOtherValue;

const aJust = Maybe.just(42);
console.log(Maybe.unwrapOrElse(handleNothing, aJust));  // 42

const aNothing = nothing<number>();
console.log(Maybe.unwrapOrElse(handleNothing, aNothing)); // 99

Type Parameters

T

T extends object

The wrapped value.

U

U

Parameters

orElseFn

() => U

A function used to generate a valid value if maybe is a Nothing.

maybe

Maybe<T>

The Maybe instance to unwrap if it is a Just

Returns

T | U

Either the content of maybe or the value returned from orElseFn.

Call Signature

unwrapOrElse<T, U>(orElseFn): (maybe) => T | U

Safely get the value out of a Maybe by returning the wrapped value if it is Just, or by applying orElseFn if it is Nothing.

This is useful when you need to generate a value (e.g. by using current values in the environment – whether preloaded or by local closure) instead of having a single default value available (as in unwrapOr).

import Maybe from 'true-myth/maybe';

// You can imagine that someOtherValue might be dynamic.
const someOtherValue = 99;
const handleNothing = () => someOtherValue;

const aJust = Maybe.just(42);
console.log(Maybe.unwrapOrElse(handleNothing, aJust));  // 42

const aNothing = nothing<number>();
console.log(Maybe.unwrapOrElse(handleNothing, aNothing)); // 99

Type Parameters

T

T extends object

The wrapped value.

U

U

Parameters

orElseFn

() => U

A function used to generate a valid value if maybe is a Nothing.

Returns

Either the content of maybe or the value returned from orElseFn.

(maybe): T | U

Parameters

maybe

Maybe<T>

Returns

T | U