/**
 * Removes the first `N` elements from an array.
 *
 * @example
 *
 * type OnlyC = DropFirst<["a", "b", "c"], 2>; // ["c"]
 */
export type DropFirst<T extends readonly unknown[], N extends number, Acc extends readonly unknown[] = []> = Length<Acc> extends N ? T : T extends [infer E1, ...infer Rest] ? DropFirst<Rest, N, [...Acc, E1]> : T;
/**
 * Can be used to filter array index types from a union of array properties.
 *
 * @example
 *
 * type OnlyItems<T> = T extends ReadonlyArray<unknown>
 *   ? { [K in Array.Index<keyof T>]: T[K] }[Array.Index<keyof T>]
 *   : never;
 */
export type Index<T> = T extends `${number}` ? T : never;
/**
 * Extracts the `length` of an array. If the value is not an array then the
 * length is `0`.
 *
 * @example
 *
 * type ArrLength = Length<["a", "b", "c"]>; // 3
 */
export type Length<T> = T extends readonly unknown[] ? T["length"] : 0;
/**
 * Tests if a value is an array. This version provides better type inference
 * than `Array.isArray`.
 *
 * @example
 *
 * isArray([]); // true
 * isArray(12); // false
 */
export declare function isArray<T, U>(value: T | U[]): value is U[];
/**
 * Sorts an array by some processor function. The processor function is called
 * for each element in the array and the return value is used to compared the
 * items using strict equality comparison.
 *
 * @example
 *
 * sortBy(["1", "5", "2", "3"], Number.parseInt); // ["1", "2", "3", "5"]
 */
export declare function sortBy<T, U>(list: T[], callback: (item: T) => U): T[];
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