All kinds of useful type helpers

type-helpers.ts

/**
 * Extracts the type of values in an object or array
 * 
 * @example
 * type Colors = {
 *   primary: string;
 *   secondary: string;
 * };
 * 
 * type ColorValue = ValueOf<Colors>; // string
 * 
 * type Numbers = number[];
 * type NumberValue = ValueOf<Numbers>; // number
 */
export type ValueOf<T> = T[keyof T];

/**
 * Allows string literal autocomplete while still accepting any string
 * 
 * @example
 * type ButtonVariant = LooseAutocomplete<'primary' | 'secondary' | 'tertiary'>;
 * 
 * // These all work:
 * const button1: ButtonVariant = 'primary';     // autocompleted
 * const button2: ButtonVariant = 'secondary';   // autocompleted
 * const button3: ButtonVariant = 'custom';      // also valid
 */
export type LooseAutocomplete<T extends string> = T | (string & {});

/**
 * Applies Omit<T, K> in a distributive way over union types
 *
 * @description
 * This type helper ensures that when using Omit with a union type, the Omit operation
 * is applied to each member of the union independently.
 *
 * @template T - The union type to distribute Omit over
 * @template K - The keys to omit from each member of the union
 *
 * @example
 * type Square = { kind: 'square'; size: number; color: string };
 * type Circle = { kind: 'circle'; radius: number; color: string };
 * type Shape = Square | Circle;
 *
 * // Regular Omit might not work as expected with discriminative unions
 * type ShapeWithoutColor1 = Omit<Shape, 'color'>;
 *
 * // DistributiveOmit properly removes 'color' from each shape
 * type ShapeWithoutColor2 = DistributiveOmit<Shape, 'color'>;
 * // Result:
 * // { kind: 'square'; size: number } | { kind: 'circle'; radius: number }
 */
export type DistributiveOmit<T, K extends keyof any> = T extends any
  ? Omit<T, K>
  : never;