Bump to v4.0.0.

union.js

@@ -0,0 +1,23 @@
+define(['./internal/baseFlatten', './internal/baseUniq', './rest'], function(baseFlatten, baseUniq, rest) {
+
+  /**
+   * Creates an array of unique values, in order, from all of the provided arrays
+   * using [`SameValueZero`](http://ecma-international.org/ecma-262/6.0/#sec-samevaluezero)
+   * for equality comparisons.
+   *
+   * @static
+   * @memberOf _
+   * @category Array
+   * @param {...Array} [arrays] The arrays to inspect.
+   * @returns {Array} Returns the new array of combined values.
+   * @example
+   *
+   * _.union([2, 1], [4, 2], [1, 2]);
+   * // => [2, 1, 4]
+   */
+  var union = rest(function(arrays) {
+    return baseUniq(baseFlatten(arrays, false, true));
+  });
+
+  return union;
+});