What is the TypeScript's alternative to ReasonML's option type?

Question

What is the TypeScript's alternative to ReasonML's option type?

When using ReasonML, the option type is a variant that can be either Some('a) or None.

If I were to represent the same concept in TypeScript, how would I go about it?

Answer 1

Answer №1

When it comes to TypeScript, there isn't a direct equivalent for certain scenarios. The approach you take will vary depending on how you intend to use it: be it as a property, function parameter, variable, or function return type...

If you are looking to use it as a property within an object/interface, one option is to utilize optional properties, like so:

interface Something {
   myProperty?: SomeType;
//           ^−−−−− flagging it as optional
}

This same concept applies to function parameters.

For variables or return types, incorporating a union type with either undefined or null can be helpful, such as:

let example: SomeType | undefined;
// or
let example: SomeType | null = null;

The former indicates that example can be of type SomeType or undefined, while the latter suggests it can be either SomeType or null. (Do note that the latter case requires an initializer, as otherwise example would default to undefined which is not a valid value for SomeType | null.)

Answer 2

When it comes to TypeScript, there isn't a direct equivalent for certain scenarios. The approach you take will vary depending on how you intend to use it: be it as a property, function parameter, variable, or function return type...

If you are looking to use it as a property within an object/interface, one option is to utilize optional properties, like so:

interface Something {
   myProperty?: SomeType;
//           ^−−−−− flagging it as optional
}

This same concept applies to function parameters.

For variables or return types, incorporating a union type with either undefined or null can be helpful, such as:

let example: SomeType | undefined;
// or
let example: SomeType | null = null;

The former indicates that example can be of type SomeType or undefined, while the latter suggests it can be either SomeType or null. (Do note that the latter case requires an initializer, as otherwise example would default to undefined which is not a valid value for SomeType | null.)

Answer 3

Answer №2

Here's an example of how you might structure it:

type Nothing = never;

type Something<T> = T;

type Option<T> = Nothing | Something<T>

If functional programming with TypeScript piques your interest, check out fp-ts

Answer 4

Here's an example of how you might structure it:

type Nothing = never;

type Something<T> = T;

type Option<T> = Nothing | Something<T>

If functional programming with TypeScript piques your interest, check out fp-ts

What is the TypeScript's alternative to ReasonML's option type?

Answer №1

Answer №2

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