type-samurai/src/shift.d.ts

Advanced utility types for Typescript

import { If } from "./if";

type ShiftOptions = {
  includeRemoved: boolean;
};

/**
 * Removes the first element from the first array argument.
 * If the `includeRemoved` option is `true` return removed element with the new array in the format of [rest, removed]
 * @example
 * ```ts
 * // [2, 3]
 * type Case1 = Shift<[1, 2, 3]>
 * // [[2, 3], 1]
 * type Case2 = Shift<[1, 2, 3], {includeRemoved: true}>
 * ```
 */
export type Shift<
  T extends readonly unknown[],
  Options extends ShiftOptions = { includeRemoved: false }
> = T extends readonly [infer Removed, ...infer Rest extends readonly unknown[]]
  ? If<Options["includeRemoved"], [Rest, Removed], Rest>
  : never;