HORIZON PROJECT

var baseFlatten = require('./_baseFlatten'),

    baseRest = require('./_baseRest'),

    baseUniq = require('./_baseUniq'),

    isArrayLikeObject = require('./isArrayLikeObject'),

    last = require('./last');

/**

 * This method is like `_.union` except that it accepts `comparator` which

 * is invoked to compare elements of `arrays`. Result values are chosen from

 * the first array in which the value occurs. The comparator is invoked

 * with two arguments: (arrVal, othVal).

 *

 * @static

 * @memberOf _

 * @since 4.0.0

 * @category Array

 * @param {...Array} [arrays] The arrays to inspect.

 * @param {Function} [comparator] The comparator invoked per element.

 * @returns {Array} Returns the new array of combined values.

 * @example

 *

 * var objects = [{ 'x': 1, 'y': 2 }, { 'x': 2, 'y': 1 }];

 * var others = [{ 'x': 1, 'y': 1 }, { 'x': 1, 'y': 2 }];

 *

 * _.unionWith(objects, others, _.isEqual);

 * // => [{ 'x': 1, 'y': 2 }, { 'x': 2, 'y': 1 }, { 'x': 1, 'y': 1 }]

 */

var unionWith = baseRest(function(arrays) {

  var comparator = last(arrays);

  comparator = typeof comparator == 'function' ? comparator : undefined;

  return baseUniq(baseFlatten(arrays, 1, isArrayLikeObject, true), undefined, comparator);

});

module.exports = unionWith;