var baseFlatten = require('../internal/baseFlatten'),
    baseUniq = require('../internal/baseUniq');

/**
 * Creates an array of unique values, in order, of the provided arrays using
 * `SameValueZero` for equality comparisons.
 *
 * **Note:** `SameValueZero` comparisons are like strict equality comparisons,
 * e.g. `===`, except that `NaN` matches `NaN`. See the
 * [ES spec](https://people.mozilla.org/~jorendorff/es6-draft.html#sec-samevaluezero)
 * for more details.
 *
 * @static
 * @memberOf _
 * @category Array
 * @param {...Array} [arrays] The arrays to inspect.
 * @returns {Array} Returns the new array of combined values.
 * @example
 *
 * _.union([1, 2], [4, 2], [2, 1]);
 * // => [1, 2, 4]
 */
function union() {
  return baseUniq(baseFlatten(arguments, false, true));
}

module.exports = union;
