isNaN.js

var isNumber = require('./isNumber');

/**
 * Checks if `value` is `NaN`.
 *
 * **Note:** This method is not the same as [`isNaN`](https://es5.github.io/#x15.1.2.4)
 * which returns `true` for `undefined` and other non-numeric values.
 *
 * @static
 * @memberOf _
 * @category Lang
 * @param {*} value The value to check.
 * @returns {boolean} Returns `true` if `value` is `NaN`, else `false`.
 * @example
 *
 * _.isNaN(NaN);
 * // => true
 *
 * _.isNaN(new Number(NaN));
 * // => true
 *
 * isNaN(undefined);
 * // => true
 *
 * _.isNaN(undefined);
 * // => false
 */
function isNaN(value) {
  // An `NaN` primitive is the only value that is not equal to itself.
  // Perform the `toStringTag` check first to avoid errors with some host objects in IE.
  return isNumber(value) && value != +value;
}

module.exports = isNaN;