opztione

Monadic Option implementation in TS

Static methods

Option.none()

Returns a None representing the absence of value (undefined, null etc.).

const none = Option.none();

Option.some()

Returns a Some wrapping the provided value.

const stringOption = Option.some('hello');

Option.of()

Returns a Some if the provided value is truthy, returns None otherwise.

const stringOption = Option.of('hello');
const none = Option.of(null);

Example

const actual = Option.of('myString')
    .map((stringValue) => stringValue.length)
    .flatMap((stringLength) => Option.of(!!stringLength))
    .peek((value) => {
        console.log('hello world', value)
    })
    .get(); // will return true

Optional API

.get()

Returns the wrapped value if this is a Some instance, will throw if this is a None.

const stringOption = Option.some('hello');
const stringValue = Option.get(); // will be 'hello'

const none = Option.none();
const value = Option.get() // will throw;

.getOrElse()

Returns the wrapped value or use the provided fallback value

const none = Option.none();
const value = Option.getOrElse("hello") // will be 'hello'

.getOrElseThrow()

Returns the wrapped value or throws if this is a None or if the wrapped value is undefined, null etc.

const stringOption = Option.some('hello');
const stringValue = Option.getOrElseThrow(new MyCustomError('oops')); // won't throw, will be 'hello'

const nullableOption = Option.some(null);
nullableOption.getOrElseThrow(new MyCustomError('oops')); // will throw

const none = Option.none();
none.getOrElseThrow(new MyCustomError('oops')); // will throw

.isEmpty()

Returns true if this is a None, false if this is a Some.

const stringOption = Option.some('hello');
const stringIsEmpty = stringOption.isEmpty() // will be false

const nullableOption = Option.none();
const isEmpty = nullableOption.isEmpty() // will be true

.isDefined()

Returns false if this is a None, true if this is a Some.

const stringOption = Option.some('hello');
const stringIsEmpty = stringOption.isEmpty() // will be false

const nullableOption = Option.none();
const isEmpty = nullableOption.isEmpty() // will be true

.flatMap()

Maps the value to a new Option if this is a Some, otherwise returns None.

const stringOption = Option.some('hello');
const newOption = stringOption.flatMap((param) => {
    return Option.of({
        some: 'value'
    });
});

newOption.get() // will return Optional<{some: string}>

const nullableOption = Option.none();
const newNoneOption = nullableOption.flatMap((param) => {
    return Option.of({
        some: 'value'
    });
});

newNoneOption.get() // will return None

.map()

Maps the value and wraps it in a new Some if this is a Some, returns None.

const stringOption = Option.some('hello');
const newOption = stringOption.map((param) => {
    return {
        some: 'value'
    };
});

newOption.get() // will return Optional<{some: string}>

const nullableOption = Option.none();
const newNoneOption = nullableOption.map((param) => {
    return {
        some: 'value'
    };
});

newNoneOption.get() // will return Optional<Nullable>

.peek()

Applies an action to this value, if this option is a Some, otherwise does nothing.

const stringOption = Option.some('hello');
const newOption = stringOption.peek((value) => {
    console.log('bye') // will be executed
});

const nullableOption = Option.none();
const newNoneOption = nullableOption.peek((value) => {
    console.log('oops') // won't be executed
});