Bump to v4.0.0.

keys.js

@@ -0,0 +1,51 @@
+define(['./internal/baseHas', './internal/baseKeys', './internal/indexKeys', './isArrayLike', './internal/isIndex', './internal/isPrototype'], function(baseHas, baseKeys, indexKeys, isArrayLike, isIndex, 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;
+  }
+
+  return keys;
+});