first_not_nullish_of.ts

// Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.
// This module is browser compatible.

/**
 * Applies the given selector to elements in the given array until a value is produced that is neither `null` nor `undefined` and returns that value
 * Returns `undefined` if no such value is produced
 *
 * Example:
 *
 * ```ts
 * import { firstNotNullishOf } from "https://deno.land/std@$STD_VERSION/collections/mod.ts";
 * import { assertEquals } from "https://deno.land/std@$STD_VERSION/testing/asserts.ts";
 *
 * const tables = [
 *     { number: 11, order: null },
 *     { number: 12, order: 'Soup' },
 *     { number: 13, order: 'Salad' },
 * ]
 * const nextOrder = firstNotNullishOf(tables, it => it.order)
 *
 * assertEquals(nextOrder, 'Soup')
 * ```
 */
export function firstNotNullishOf<T, O>(
  array: readonly T[],
  selector: (item: T) => O | undefined | null,
): NonNullable<O> | undefined {
  for (const current of array) {
    const selected = selector(current);

    if (selected !== null && selected !== undefined) {
      return selected as NonNullable<O>;
    }
  }

  return undefined;
}