ByIndex

ByIndex.ts

/**
 * Converts array or tuple `T` to an object with keys as indices and values as element types.
 * It's handy for when you need type-safe access based on indices, especially with tuples.
 * 
 * `ByIndex` is useful over `{ [K in keyof T]: T[K] }` for:
 * - Keeping index keys as strings for object mapping from tuples.
 * - Handling arrays as tuples for a unified index-based object structure.
 * 
 * Example:
 * type ExampleTuple = ByIndex<[string, number]>; // { "0": string, "1": number }
 * type ExampleArray = ByIndex<(string | number)[]>; // { [x: number]: string | number }
 * 
 * It's a small utility that ensures your data structures remain type-safe, even with dynamic indexing.
 */
type ByIndex<T extends any[]> = {
  [K in keyof T as T extends [any, ...any[]]
    ? K extends `${number}`
      ? K
      : never
    : number]: K extends `${number}` | number ? T[K] : never;
};