Bump to v4.3.0.

isWeakSet.js

@@ -0,0 +1,35 @@
+import isObjectLike from './isObjectLike';
+
+/** `Object#toString` result references. */
+var weakSetTag = '[object WeakSet]';
+
+/** Used for built-in method references. */
+var objectProto = Object.prototype;
+
+/**
+ * Used to resolve the [`toStringTag`](http://ecma-international.org/ecma-262/6.0/#sec-object.prototype.tostring)
+ * of values.
+ */
+var objectToString = objectProto.toString;
+
+/**
+ * Checks if `value` is classified as a `WeakSet` object.
+ *
+ * @static
+ * @memberOf _
+ * @category Lang
+ * @param {*} value The value to check.
+ * @returns {boolean} Returns `true` if `value` is correctly classified, else `false`.
+ * @example
+ *
+ * _.isWeakSet(new WeakSet);
+ * // => true
+ *
+ * _.isWeakSet(new Set);
+ * // => false
+ */
+function isWeakSet(value) {
+  return isObjectLike(value) && objectToString.call(value) == weakSetTag;
+}
+
+export default isWeakSet;