Bump to v4.0.0.

union.js

@@ -0,0 +1,24 @@
+var baseFlatten = require('./internal/baseFlatten'),
+    baseUniq = require('./internal/baseUniq'),
+    rest = require('./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));
+});
+
+module.exports = union;