isThenable.js

import { pathSatisfies } from 'ramda';

import isFunction from './isFunction';


/**
 * Checks if input value is a `thenable`.
 * `thenable` is an object or function that defines a `then` method.
 *
 * @func isThenable
 * @memberOf RA
 * @since {@link https://char0n.github.io/ramda-adjunct/2.1.0|v2.1.0}
 * @category Type
 * @sig * -> Boolean
 * @param {*} val The value to test
 * @return {Boolean}
 * @see {@link RA.isPromise|isPromise}
 * @example
 *
 * RA.isThenable(null); // => false
 * RA.isThenable(undefined); // => false
 * RA.isThenable([]); // => false
 * RA.isThenable(Promise.resolve()); // => true
 * RA.isThenable(Promise.reject()); // => true
 * RA.isThenable({ then: () => 1 }); // => true
 */
const isThenable = pathSatisfies(isFunction, ['then']);

export default isThenable;