option-t

option-t

• This library represents Option type in ECMAScript.
• APIs are inspired by Rust Language's Option<T>.

Installation

npm install --save option-t

Usage

var OptionT = require('option-t');

// `Some<T>`
var some = new OptionT.Some(1);
console.log(some.isSome); // true
console.log(some.unwrap()); // 1

// `None`
var none = new OptionT.None();
console.log(none.isSome); // false
console.log(none.unwrap()); // this will throw `Error`.

JSON Representation

Some<T>

new Some(1) will be:

{
    "is_some": true,
    "value": 1
}

None

new None() will be:

{
    "is_some": false
}

API

• Type Definition
• Implementation: See inline JSDoc.
  • Option<T>

Semantics

This library represents Option type in ECMAScript. So this object will be the one of following states:

• Some<T>
  • option instanceof OptionT.Some
  • option.isSome === true.
• None
  • option instanceof OptionT.None
  • option.isSome === false.

Option<T>

This type is a interface to represent Option<T>. Some<T> and None must implement this Option<T> interface.

This is just interface. This is not exported to an environment which has no interface feature as a part of its type system like TypeScript.

If you'd like to check whether the object option is Option<T> or not in such an environment, you can use option instanceof OptionT.OptionT to check it.

But this way is not a tier-1 approach. We recommend to use a interface and type system strongly. Thus we don't export OptionT object to the type definition for TypeScript.

Some<T>

This type represents that there are some values T. If this value wraps null, it just means that there is a null value.

None (None<T>)

This type represents that there is no value explicitly. It is just None !== null.

License

MIT License