text: define(['./internal/baseFlatten', './internal/baseIteratee', './internal/baseUniq', './isArrayLikeObject', './last', './rest'], function(baseFlatten, baseIteratee, baseUniq, isArrayLikeObject, last, rest) {
  
    /** Used as a safe reference for `undefined` in pre-ES5 environments. */
    var undefined;
  
    /**
     * This method is like `_.union` except that it accepts `iteratee` which is
     * invoked for each element of each `arrays` to generate the criterion by which
     * uniqueness is computed. The iteratee is invoked with one argument: (value).
     *
     * @static
     * @memberOf _
     * @category Array
     * @param {...Array} [arrays] The arrays to inspect.
     * @param {Function|Object|string} [iteratee=_.identity] The iteratee invoked per element.
     * @returns {Array} Returns the new array of combined values.
     * @example
     *
     * _.unionBy([2.1, 1.2], [4.3, 2.4], Math.floor);
     * // => [2.1, 1.2, 4.3]
     *
     * // using the `_.property` iteratee shorthand
     * _.unionBy([{ 'x': 1 }], [{ 'x': 2 }, { 'x': 1 }], 'x');
     * // => [{ 'x': 1 }, { 'x': 2 }]
     */
    var unionBy = rest(function(arrays) {
      var iteratee = last(arrays);
      if (isArrayLikeObject(iteratee)) {
        iteratee = undefined;
      }
      return baseUniq(baseFlatten(arrays, false, true), baseIteratee(iteratee));
    });
  
    return unionBy;
  });
  