iron-enum

Iron Enum

Finally Rust like enums in Typescript!

• Ergonomic AF!
• Fully type safe!
• Only 500 bytes!

| Github | NPM | JSR |

Typescript enums only provide simple variants:

enum Shape {
    Square,
    Circle
}

But what if you wanted to provide data for each variant that is context specific? Well now you can!

import { IronEnum } from "iron-enum";

const ShapeEnum = IronEnum<{
    Empty: {},
    Square: { width: number, height: number },
    Circle: { radius: number }
}>();

const exampleShape = ShapeEnum.Square({width: 22, height: 50});

// Supports matching
exampleShape.match({
    Empty: () => {
        // runs if the shape is empty
    },
    Square: ({width, height}) => {
        // runs if the shape is square
    },
    Circle: ({radius}) => {
        // runs if the shape is circle
    }
});

// Supports fallback cases and returns through match
const result = exampleShape.match({
    Square: ({width, height}) => {
        // runs if the shape is square
        return width;
    },
    _: () => {
        // runs if it's anything but a square
        return "hello"
    }
});
// result type is inherited from match arm return types.
// typeof result == number | string

if (exampleShape.if.Square()) {
    // runs if the shape is a square
}

if (exampleShape.ifNot.Square()) {
    // runs if the shape is NOT a square
}

console.log(exampleShape.unwarp())
// output: ["Square", { width: 22, height: 50 }]

// this method will only allow ShapeEnum variants as an argument
const someFn = (onlyShapeEnum: typeof ShapeEnum._self.prototype) => {

}

Just like in Rust, the .match(...) keys must contain a callback for each variant OR provide a fallback method with a _ property. Failing this constraint leads to a type error.

Changelog

1.0.1 - Oct 9, 2024

• Initial release.