defaultTo.ts

// Copyright (c) 2020 Jozty. All rights reserved. MIT license.

import curryN from './utils/curry_n.ts';

// @types
type DefaultTo_2<T1> = <T2>(value: T2) => T1 | T2;

type DefaultTo =
  & (<T1>(defaultV: T1) => DefaultTo_2<T1>)
  & (<T1, T2>(defaultV: T1, value: T2) => T1 | T2);

function _defaultTo<T1, T2>(defaultV: T1, value: T2) {
  return value == null || value !== value ? defaultV : value;
}

/**
 * Returns the second argument if it is not `null`, `undefined` or `NaN`;
 * otherwise the first argument is returned.
 *
 *      const defaultTo125 = Fae.defaultTo(125)
 *
 *      defaultTo125(null)  //=> 125
 *      defaultTo125(undefined)  //=> 125
 *      defaultTo125(false)  //=> false
 *      defaultTo125('Fae')  //=> 'Fae'
 */
export const defaultTo = curryN(2, _defaultTo) as DefaultTo;