True Myth / maybe / or

Function: or()

Call Signature

or<T>(defaultMaybe, maybe): Maybe<T>

Provide a fallback for a given Maybe. Behaves like a logical or: if the maybe value is a Just, returns that maybe; otherwise, returns the defaultMaybe value.

This is useful when you want to make sure that something which takes a Maybe always ends up getting a Just variant, by supplying a default value for the case that you currently have a nothing.

import Maybe from 'true-utils/maybe';

const justA = Maybe.just("a");
const justB = Maybe.just("b");
const aNothing: Maybe<string> = nothing();

console.log(Maybe.or(justB, justA).toString());  // Just(A)
console.log(Maybe.or(aNothing, justA).toString());  // Just(A)
console.log(Maybe.or(justB, aNothing).toString());  // Just(B)
console.log(Maybe.or(aNothing, aNothing).toString());  // Nothing

Type Parameters

T

T extends object

The type of the wrapped value.

Parameters

defaultMaybe

Maybe<T>

The Maybe to use if maybe is a Nothing.

maybe

Maybe<T>

The Maybe instance to evaluate.

Returns

Maybe<T>

maybe if it is a Just, otherwise defaultMaybe.

Call Signature

or<T>(defaultMaybe): (maybe) => Maybe<T>

Provide a fallback for a given Maybe. Behaves like a logical or: if the maybe value is a Just, returns that maybe; otherwise, returns the defaultMaybe value.

This is useful when you want to make sure that something which takes a Maybe always ends up getting a Just variant, by supplying a default value for the case that you currently have a nothing.

import Maybe from 'true-utils/maybe';

const justA = Maybe.just("a");
const justB = Maybe.just("b");
const aNothing: Maybe<string> = nothing();

console.log(Maybe.or(justB, justA).toString());  // Just(A)
console.log(Maybe.or(aNothing, justA).toString());  // Just(A)
console.log(Maybe.or(justB, aNothing).toString());  // Just(B)
console.log(Maybe.or(aNothing, aNothing).toString());  // Nothing

Type Parameters

T

T extends object

The type of the wrapped value.

Parameters

defaultMaybe

Maybe<T>

The Maybe to use if maybe is a Nothing.

Returns

maybe if it is a Just, otherwise defaultMaybe.

(maybe) => Maybe<T>