Bump to v4.0.0.

assignIn.js

@@ -0,0 +1,38 @@
+var copyObject = require('./internal/copyObject'),
+    createAssigner = require('./internal/createAssigner'),
+    keysIn = require('./keysIn');
+
+/**
+ * This method is like `_.assign` except that it iterates over own and
+ * inherited source properties.
+ *
+ * **Note:** This method mutates `object`.
+ *
+ * @static
+ * @memberOf _
+ * @alias extend
+ * @category Object
+ * @param {Object} object The destination object.
+ * @param {...Object} [sources] The source objects.
+ * @returns {Object} Returns `object`.
+ * @example
+ *
+ * function Foo() {
+ *   this.b = 2;
+ * }
+ *
+ * function Bar() {
+ *   this.d = 4;
+ * }
+ *
+ * Foo.prototype.c = 3;
+ * Bar.prototype.e = 5;
+ *
+ * _.assignIn({ 'a': 1 }, new Foo, new Bar);
+ * // => { 'a': 1, 'b': 2, 'c': 3, 'd': 4, 'e': 5 }
+ */
+var assignIn = createAssigner(function(object, source) {
+  copyObject(source, keysIn(source), object);
+});
+
+module.exports = assignIn;