diff --git a/js/doc/maps/rainbow.js b/js/doc/maps/rainbow.js
new file mode 100644
index 0000000..6a8ba5b
--- /dev/null
+++ b/js/doc/maps/rainbow.js
@@ -0,0 +1,13 @@
+var colors = Require('doc/colors');
+
+module['exports'] = (function () {
+  var rainbowColors = ['red', 'yellow', 'green', 'blue', 'magenta']; //RoY G BiV
+  return function (letter, i, exploded) {
+    if (letter === " ") {
+      return letter;
+    } else {
+      return colors[rainbowColors[i++ % rainbowColors.length]](letter);
+    }
+  };
+})();
+