Typescript version of fsharps Option module

Usage no npm install needed!

<script type="module">
  import adrielusOption from 'https://cdn.skypack.dev/@adrielus/option';


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Probably the most opinionated implementation of the Option type for TypeScript.


  • Lazy and async versions of helpers: One of the goals of this lib is to provide variations of helpers which are lazy (don't compute something if it's not needed) or async (make mixing Promises and Options easier). If there is any function you want one of those variations of, be sure to open an issue:)
  • Large amount of helpers (curently 30), more than f#'s and elm's core libraries combined.
  • Typesafe:
    const foo0: Option<string> = None // works
    const foo1: Option<string> = Some('foo1') // works
    const foo2: Option<string> = 'foo2' // errors out
    const foo3: Option<string> = null // errors out
    const foo4: Option<string> = Some(4) // errors out
  • Reference equality:
    Some(7) === Some(7) // true
    Some(7) === Some(5) // false
    Some(7) === None // false


Both limitaions bellow come from the lack of nominal-typing offered by TypeScript and are inherited from the Brand type offered by the utility-types library

  • Due to the way the library works (using the Brand type from utility-types) Some(4) === 4 will return true, similarly to how 4 == "4" returns true (except in this libraries case the === operator will behave the same way).
  • The inner value of Option cannot have a __brand prop (well, tehnically it can but it would be overwritten by the Brand type from utility-types)


npm install @adrielus/option

(There is also an amd build at /dist/bundle.umd.js which uses the Option namespace)


For detailed usage read the docs

Note: The docs are still work in progress. Contributions are welcome:)


First, clone this repo:

git clone https://github.com/Mateiadrielrafael/option
cd option

Then use pnpm to install the dependencies:

pnpm install

You can use the build command to build the package (this is dont automatically by github actions):

pnpm run build