diff --git a/Libraries/Utilities/__tests__/mapWithSeparator-test.js b/Libraries/Utilities/__tests__/mapWithSeparator-test.js
new file mode 100644
index 0000000000..4dea1ec7bf
--- /dev/null
+++ b/Libraries/Utilities/__tests__/mapWithSeparator-test.js
@@ -0,0 +1,57 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ */
+'use strict';
+
+jest.unmock('mapWithSeparator');
+
+describe('mapWithSeparator', () => {
+  const mapWithSeparator = require('mapWithSeparator');
+
+  it('mapWithSeparator returns expected results', () => {
+    const array = [1, 2, 3];
+    const result = mapWithSeparator(
+      array,
+      function(value) {
+        return value * 2;
+      },
+      function() {
+        return 0;
+      }
+    );
+    expect(result).toEqual([2, 0, 4, 0, 6]);
+  });
+
+  it('mapWithSeparator indices are correct', () => {
+    const array = [1, 2, 3];
+    const result = mapWithSeparator(
+      array,
+      function(value, index) {
+        return index;
+      },
+      function(index) {
+        return index;
+      }
+    );
+    expect(result).toEqual([0, 0, 1, 1, 2]);
+  });
+
+  it('mapWithSeparator passes correct array and indices', () => {
+    const array = [3, 2, 1];
+    const result = mapWithSeparator(
+      array,
+      function(value, index, arr) {
+        return arr[index];
+      },
+      function(index) {
+        return index;
+      }
+    );
+    expect(result).toEqual([3, 0, 2, 1, 1]);
+  });
+});
diff --git a/Libraries/Utilities/mapWithSeparator.js b/Libraries/Utilities/mapWithSeparator.js
index 4aa8665c35..ff3048a260 100644
--- a/Libraries/Utilities/mapWithSeparator.js
+++ b/Libraries/Utilities/mapWithSeparator.js
@@ -1,19 +1,29 @@
 /**
- * Copyright 2004-present Facebook. All Rights Reserved.
+ * Copyright (c) 2015-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
  *
  * @providesModule mapWithSeparator
+ * @flow
  */
 'use strict';
 
-function mapWithSeparator(array, valueFunction, separatorFunction) {
-  var results = [];
-  for (var i = 0; i < array.length; i++) {
-    results.push(valueFunction(array[i], i, array));
-    if (i !== array.length - 1) {
-      results.push(separatorFunction(i));
+function mapWithSeparator<TFrom, TTo>(
+  items: Array<TFrom>,
+  itemRenderer: (item: TFrom, index: number, items: Array<TFrom>) => TTo,
+  spacerRenderer: (index: number) => TTo,
+): Array<TTo> {
+  const mapped = [];
+  if (items.length > 0) {
+    mapped.push(itemRenderer(items[0], 0, items));
+    for (let ii = 1; ii < items.length; ii++) {
+      mapped.push(spacerRenderer(ii - 1), itemRenderer(items[ii], ii, items));
     }
   }
-  return results;
+  return mapped;
 }
 
 module.exports = mapWithSeparator;