Bump to v4.0.0.

keys.js

@@ -0,0 +1,55 @@
+import baseHas from './internal/baseHas';
+import baseKeys from './internal/baseKeys';
+import indexKeys from './internal/indexKeys';
+import isArrayLike from './isArrayLike';
+import isIndex from './internal/isIndex';
+import isPrototype from './internal/isPrototype';
+
+/**
+ * Creates an array of the own enumerable property names of `object`.
+ *
+ * **Note:** Non-object values are coerced to objects. See the
+ * [ES spec](http://ecma-international.org/ecma-262/6.0/#sec-object.keys)
+ * for more details.
+ *
+ * @static
+ * @memberOf _
+ * @category Object
+ * @param {Object} object The object to query.
+ * @returns {Array} Returns the array of property names.
+ * @example
+ *
+ * function Foo() {
+ *   this.a = 1;
+ *   this.b = 2;
+ * }
+ *
+ * Foo.prototype.c = 3;
+ *
+ * _.keys(new Foo);
+ * // => ['a', 'b'] (iteration order is not guaranteed)
+ *
+ * _.keys('hi');
+ * // => ['0', '1']
+ */
+function keys(object) {
+  var isProto = isPrototype(object);
+  if (!(isProto || isArrayLike(object))) {
+    return baseKeys(object);
+  }
+  var indexes = indexKeys(object),
+      skipIndexes = !!indexes,
+      result = indexes || [],
+      length = result.length;
+
+  for (var key in object) {
+    if (baseHas(object, key) &&
+        !(skipIndexes && (key == 'length' || isIndex(key, length))) &&
+        !(isProto && key == 'constructor')) {
+      result.push(key);
+    }
+  }
+  return result;
+}
+
+export default keys;