Either<TLeft, TRight> (class)

Either represents values with two possibilities: TLeft value of type Either TLeft/TRight is either Left TLeft or Right TRight.

Status: stable

Factory Methods

Either.left<T>(value)

Creates a left Either instance with the left value filled.

Status: stable
Returns: Either<T, unknown>

Parameters

Name	Type	Description
value	T	The value to fill the left slot

Example usage

const { Either } = Melon.std.functional;

const myValue: Either<string, number> = condition 
    ? Either.left("Hello") : Either.right(100);

Either.right<T>(value)

Creates a right Either instance with the right value filled.

Status: stable
Returns: Either<unknown, T>

Parameters

Name	Type	Description
value	T	The value to fill the left slot

Example usage

const { Either } = Melon.std.functional;

const myValue: Either<string, number> = condition 
    ? Either.left("Hello") : Either.right(100);

Instance Methods

Either.fold<T>(actionLeft, actionRight)

Create an a pattern-matching based operation chain to the Either values.

Status: stable
Returns: T

Parameters

Name	Type	Description
actionLeft	Function	The operation to be called in case of the left value not being null
actionRight	Function	The operation to be called in case of the right value not being null

Example usage

const { Either } = Melon.std.functional;

const myValue: Either<string, number> = condition 
    ? Either.left("Hello") : Either.right(100);

const myDerivedValue = myValue.fold<string[]>(
    left => left.split(), 
    right => right.toString().split()
);