To be clear that we set a new variable

js/README.md

diff --git a/js/README.md b/js/README.md
index 24386dc..ef0d4b1 100644
--- a/js/README.md
+++ b/js/README.md
@@ -158,7 +158,7 @@
     message.setPhoneNumbers(["800-555-1212", "800-555-0000"]);
 
     // Serializes to a UInt8Array.
-    bytes = message.serializeBinary();
+    var bytes = message.serializeBinary();
 
     var message2 = MyMessage.deserializeBinary(bytes);