Getting started

TypeFoundry helps you build TypeScript types for APIs with multiple states. It generates a discriminated union from the variants you define.

Install

npm install typefoundry

TypeFoundry provides types only. It does not add runtime code or validate values.

Define your first type

Import TypeFoundry as a type and describe the available options:

import type { TypeFoundry } from "typefoundry";

type ButtonProps = TypeFoundry<{
  variants: {
    size: {
      small: { padding: 4 };
      large: { padding: 12 };
    };
  };
}>;

This is equivalent to:

type ButtonProps =
  | { size: "small"; padding: 4 }
  | { size: "large"; padding: 12 };

TypeScript can narrow the type based on the selected option:

function getPadding(props: ButtonProps) {
  if (props.size === "small") {
    return props.padding; // 4
  }

  return props.padding; // 12
}

Next steps

• Read the guide to learn about common properties, extending types, and references.
• See the API reference for details on each exported type.