isNaN.js

import { curryN } from 'ramda';

import isFunction from './isFunction';
import polyfill from './internal/polyfills/Number.isNaN';

export const isNaNPolyfill = curryN(1, polyfill);

/**
 * Checks whether the passed value is `NaN` and its type is `Number`.
 * It is a more robust version of the original, global isNaN().
 *
 *
 * @func isNaN
 * @memberOf RA
 * @since {@link https://char0n.github.io/ramda-adjunct/0.6.0|v0.6.0}
 * @category Type
 * @sig * -> Boolean
 * @param {*} val The value to test
 * @return {boolean}
 * @see {@link RA.isNotNaN|isNotNaN}
 * @example
 *
 * RA.isNaN(NaN); // => true
 * RA.isNaN(Number.NaN); // => true
 * RA.isNaN(0 / 0); // => true
 *
 * // e.g. these would have been true with global isNaN().
 * RA.isNaN('NaN'); // => false
 * RA.isNaN(undefined); // => false
 * RA.isNaN({}); // => false
 * RA.isNaN('blabla'); // => false
 *
 * RA.isNaN(true); // => false
 * RA.isNaN(null); // => false
 * RA.isNaN(37); // => false
 * RA.isNaN('37'); // => false
 * RA.isNaN('37.37'); // => false
 * RA.isNaN(''); // => false
 * RA.isNaN(' '); // => false
 */
const _isNaN = isFunction(Number.isNaN)
  ? curryN(1, Number.isNaN)
  : isNaNPolyfill;

export default _isNaN;