negate.js

/** Error message constants. */
var FUNC_ERROR_TEXT = 'Expected a function';

/**
 * Creates a function that negates the result of the predicate `func`. The
 * `func` predicate is invoked with the `this` binding and arguments of the
 * created function.
 *
 * @static
 * @memberOf _
 * @since 3.0.0
 * @category Function
 * @param {Function} predicate The predicate to negate.
 * @returns {Function} Returns the new negated function.
 * @example
 *
 * function isEven(n) {
 *   return n % 2 == 0;
 * }
 *
 * _.filter([1, 2, 3, 4, 5, 6], _.negate(isEven));
 * // => [1, 3, 5]
 */
function negate(predicate) {
  if (typeof predicate != 'function') {
    throw new TypeError(FUNC_ERROR_TEXT);
  }
  return function() {
    var args = arguments;
    switch (args.length) {
      case 0: return !predicate.call(this);
      case 1: return !predicate.call(this, args[0]);
      case 2: return !predicate.call(this, args[0], args[1]);
      case 3: return !predicate.call(this, args[0], args[1], args[2]);
    }
    return !predicate.apply(this, args);
  };
}

module.exports = negate;