Class OptionalValue<T>

A TypeScript implementation inspired by Java's Optional, designed as a container object that may or may not contain a non-null value. It offers methods for handling the value's presence or absence in a more expressive and safer way, aiming to reduce the chances of null pointer exceptions.

Type Parameters

T
The type of the value that may be contained within.

Index

Constructors

`Protected`constructor

new OptionalValue<T>(value: T): OptionalValue<T>
Protected
Initializes a new instance with the provided value, which can be null or undefined.
Type Parameters
- T
 The type of the value that may be contained within.
Parameters
- value: T
 The initial value, potentially null or undefined. to prevent direct instantiation from outside the class.
Returns OptionalValue<T>
- Defined in index.ts:31

Methods

contains

contains<U, const V>(this: Optional, value: V): this is Present<V>
Checks if the contained value matches the provided value.
Type Parameters
- U
 The type of the value contained within the current instance.
- const V
 The type of the value to check for equality.
Parameters
- this: Optional
- value: V
 The value to compare against.
Returns this is Present<V>
true if the contained value matches the provided value; otherwise, false.
Example
```
const optional: Optional<number> = Optional(123);
if (optional.contains(123)) {
 const copy: Optional.Present<123> = optional;
 const value: 123 = optional.get();
}
```
- Defined in index.ts:434

equals

equals<U, const V>(
 this: Optional,
 other: Optional<V>,
 comparator?: (a: U, b: U) => boolean,
): this is Optional<V>
Checks whether this instance is equal to another, optionally using a custom comparator.
Type Parameters
- U
 The type of the value contained within the current instance.
- const V
 The type of the value contained within the other instance.
Parameters
- this: Optional
- other: Optional<V>
 The other instance to compare.
- Optionalcomparator: (a: U, b: U) => boolean
 An optional function to compare the values.
Returns this is Optional<V>
true if both instances are equal; otherwise, false.
Example
```
const optional1: Optional<number> = Optional(123);
const optioanl2: Optional<number> = Optional(123);

if (optional1.equals(optioanl2)) {
 const copy: Optional<number> = optional1;
 const value: number | null = optional1.get();
}
```
- Defined in index.ts:397

filter

filter(
this: Optional,
predicate: (value: NonNullable) => boolean,
): Optional
Applies a predicate to the contained value if present, returning an instance containing the value only if the predicate is satisfied.
Type Parameters
- U
 The type of the value that may be contained within.
Parameters
- this: Optional
- predicate: (value: NonNullable) => boolean
 A predicate function to apply to the contained value.
Returns Optional
An instance containing the value if the predicate is satisfied; otherwise, an instance representing no value.
See
Java Reference: public Optional<T> filter(Predicate<? super T> predicate)
Example
```
const optional: Optional<number> = Optional(123);
const filtered: Optional<number> = optional.filter((value) => value > 3);
```
- Defined in index.ts:233

flatMap

flatMap<U, V>(
this: Optional,
mapper: (value: NonNullable) => Optional<V>,
): Optional<V>
Applies a flat-mapping function to the contained value if present, returning the direct result of the function without additional wrapping.
Type Parameters
- U
 The type of the value that may be contained within.
- V
 The type of the value that may be contained within the result of the mapping function.
Parameters
- this: Optional
- mapper: (value: NonNullable) => Optional<V>
 A flat-mapping function to apply to the contained value.
Returns Optional<V>
The result of the mapping function, or an instance representing no value if the original instance does not contain a value.
See
Java Reference: public Optional flatMap(Function<? super T,Optional> mapper)
Example
```
const optional: Optional<number> = Optional(123);
const flatMapped: Optional<string> = optional.flatMap((value) => Optional(String(value)));
```
- Defined in index.ts:294

get

get(): T
Retrieves the contained value.

Returns T
The contained value, which may be null if no value is present.
See
Java Reference: public T get()
Example
```
const optional: Optional<number> = Optional(123);
const value: number | null = optional.get();
```
- Defined in index.ts:126

ifEmpty

ifEmpty(consumer: () => void): this
Executes a given function if no value is contained within.
Parameters
- consumer: () => void
 A function to execute if no value is present.
Returns this
Example
```
const optional: Optional<number> = Optional(123);
optional.ifEmpty(() => console.log("Empty"));
```
- Defined in index.ts:208

ifPresent

ifPresent(consumer: (value: NonNullable<T>) => void): this
Executes a given function with the contained value if present; does nothing otherwise.
Parameters
- consumer: (value: NonNullable<T>) => void
 A function to execute with the contained value.
Returns this
See
Java Reference: public void ifPresent(Consumer<? super T> consumer)
Example
```
const optional: Optional<number> = Optional(123);
optional.ifPresent((value) => console.log("Present:", value));
```
- Defined in index.ts:168

isEmpty

isEmpty(): this is Empty

Determines whether the instance does not contain a value.

Returns this is Empty

true if no value is present; otherwise, false.

Example

const optional: Optional<number> = Optional(123);
if (optional.isEmpty()) {
  const copy: Optional.Empty = optional;
  const value: null = optional.get();
} else {
  const copy: Optional.Present<number> = optional;
  const value: number = optional.get();
}

isPresent

isPresent(): this is Present<T>

Checks whether a value is contained within.

Returns this is Present<T>

true if a value is present; otherwise, false.

See

Java Reference: public boolean isPresent()

Example

const optional: Optional<number> = Optional(123);
if (optional.isPresent()) {
  const copy: Optional.Present<number> = optional;
  const value: number = optional.get();
} else {
  const copy: Optional.Empty = optional;
  const value: null = optional.get();
}

map

map<U, V>(this: Optional, mapper: (value: NonNullable) => V): Optional<V>
Applies a mapping function to the contained value if present, wrapping the result in a new instance if the result is non-null.
Type Parameters
- U
 The type of the value that may be contained within.
- V
 The type of the value that may be contained within the result of the mapping function.
Parameters
- this: Optional
- mapper: (value: NonNullable) => V
 A function to apply to the contained value.
Returns Optional<V>
An instance containing the result of the mapping function if the result is non-null; otherwise, an instance representing no value.
See
Java Reference: public Optional map(Function<? super T,? extends U> mapper)
Example
```
const optional: Optional<number> = Optional(123);
const mapped: Optional<string> = optional.map((value) => String(value));
```
- Defined in index.ts:263

orElse

orElse(this: Optional, other: NonNullable): NonNullable
Retrieves the contained value if present; otherwise, returns a specified alternative value.
Type Parameters
- U
 The type of the value that may be contained within.
Parameters
- this: Optional
- other: NonNullable
 The alternative value to return if no value is contained.
Returns NonNullable
The contained value if present; otherwise, the alternative value.
See
Java Reference: public T orElse(T other)
Example
```
const optional: Optional<number> = Optional(123);
const orElse: number = optional.orElse(456);
```
- Defined in index.ts:317

orElseGet

orElseGet(this: Optional, other: () => NonNullable): NonNullable
Retrieves the contained value if present; otherwise, invokes a supplier function and returns its result.
Type Parameters
- U
 The type of the value that may be contained within.
Parameters
- this: Optional
- other: () => NonNullable
 A supplier function providing an alternative value.
Returns NonNullable
The contained value if present; otherwise, the result of the supplier function.
See
Java Reference: public T orElseGet(Supplier<? extends T> other)
Example
```
const optional: Optional<number> = Optional(123);
const orElseGet: number = optional.orElseGet(() => 456);
```
- Defined in index.ts:340

orElseThrow

orElseThrow<E extends Error>(
messageOrErrorSupplier?: string | () => E,
): NonNullable<T>
Retrieves the contained value if present; otherwise, throws an error provided by a supplier or a message.
Type Parameters
- E extends Error
 type of the Error to be thrown.
Parameters
- OptionalmessageOrErrorSupplier: string | () => E
 A string message or a supplier function that provides the error to be thrown.
Returns NonNullable<T>
The contained value if present; otherwise, throws the supplied error.
See
Java Reference: public <X extends Throwable> T orElseThrow(Supplier<? extends X> exceptionSupplier) throws X extends Throwable

Throws
An error if the value is not present.
Example
```
const optional: Optional<number> = Optional(123);
try {
 const value: number = optional.orElseThrow();
} catch (error) {
 console.error(error); // Error: Value not present.
}
```
- Defined in index.ts:369

toPromise

toPromise<E extends Error>(
messageOrErrorSupplier?: string | () => E,
): Promise<NonNullable<T>>
Converts the instance to a Promise.
Type Parameters
- E extends Error
Parameters
- OptionalmessageOrErrorSupplier: string | () => E
 A string message or a supplier function that provides the error if the value is empty.
Returns Promise<NonNullable<T>>
A Promise that resolves with the contained value or rejects with the error.
Example
```
const optional: Optional<number> = Optional(123);
const promise: Promise<number> = optional.toPromise();
```
- Defined in index.ts:450

toString

toString(): string

Converts the instance to a string representation.

Returns string

A string representing the contained value or empty.

Example

const optional1 = Optional(123);
console.log(optional1.toString()); // "Optional.Present<123>"

const optional2 = OptionalValue.empty();
console.log(optional2.toString()); // "Optional.Empty"

`Static`empty

empty(): Empty
Creates an instance without any contained value.

Returns Empty
An instance representing the absence of any value.
Example
```
const optional: Optional.Empty = Optional.empty();
```
- Defined in index.ts:54

`Static`isPresent

isPresent<T>(value: T): value is NonNullable<T>
Determines whether the provided value is neither null nor undefined.
Type Parameters
- T
 The type of the value that may be contained within.
Parameters
- value: T
 The value to check.
Returns value is NonNullable<T>
true if the value is present; otherwise, false.
- Defined in index.ts:40

`Static`of

of<T>(value: T): Optional<NonNullable<T>>
Wraps a given value in an instance if the value is non-null; otherwise, returns an instance representing no value.
Type Parameters
- T
 The type of the value that may be contained within.
Parameters
- value: T
 The possibly-null value to wrap.
Returns Optional<NonNullable<T>>
An instance containing the value if non-null; otherwise, an instance representing no value.
See
Java Reference: public static <T> Optional<T> of(T value)
Example
```
const optional: Optional<number> = OptionalValue.of(123);
```
Example
```
const optionalString: Optional<string> = OptionalValue.of("123" as string | undefined | null);
const optionalNull: Optional.Empty = OptionalValue.of(null);
const optionalUndefined: Optional.Empty = OptionalValue.of(undefined);
```
- Defined in index.ts:81

Class OptionalValue<T>

Type Parameters

Index

Constructors

Methods

Constructors

Protectedconstructor

Type Parameters

Parameters

Returns OptionalValue<T>

Methods

contains

Type Parameters

Parameters

Returns this is Present<V>

Example

equals

Type Parameters

Parameters

Returns this is Optional<V>

Example

filter

Type Parameters

Parameters

Returns Optional<U>

See

Example

flatMap

Type Parameters

Parameters

Returns Optional<V>

See

Example

get

Returns T

See

Example

ifEmpty

Parameters

Returns this

Example

ifPresent

Parameters

Returns this

See

Example

isEmpty

Returns this is Empty

Example

isPresent

Returns this is Present<T>

See

Example

map

Type Parameters

Parameters

Returns Optional<V>

See

Example

orElse

Type Parameters

Parameters

Returns NonNullable<U>

See

Example

orElseGet

Type Parameters

Parameters

Returns NonNullable<U>

See

Example

orElseThrow

Type Parameters

Parameters

Returns NonNullable<T>

See

Throws

Example

toPromise

Type Parameters

`Protected`constructor

`Static`empty

`Static`isPresent

`Static`of