Bump to v4.0.0.

internal/baseKeysIn.js

@@ -0,0 +1,36 @@
+import Reflect from './Reflect';
+import iteratorToArray from './iteratorToArray';
+
+/** Used for built-in method references. */
+var objectProto = Object.prototype;
+
+/** Built-in value references. */
+var enumerate = Reflect ? Reflect.enumerate : undefined,
+    propertyIsEnumerable = objectProto.propertyIsEnumerable;
+
+/**
+ * The base implementation of `_.keysIn` which doesn't skip the constructor
+ * property of prototypes or treat sparse arrays as dense.
+ *
+ * @private
+ * @param {Object} object The object to query.
+ * @returns {Array} Returns the array of property names.
+ */
+function baseKeysIn(object) {
+  object = object == null ? object : Object(object);
+
+  var result = [];
+  for (var key in object) {
+    result.push(key);
+  }
+  return result;
+}
+
+// Fallback for IE < 9 with es6-shim.
+if (enumerate && !propertyIsEnumerable.call({ 'valueOf': 1 }, 'valueOf')) {
+  baseKeysIn = function(object) {
+    return iteratorToArray(enumerate(object));
+  };
+}
+
+export default baseKeysIn;