Fix received keyword

readMessageBegin doesn't declare received as a variable.
diff --git a/lib/js/src/thrift.js b/lib/js/src/thrift.js
index 0c4eb26..c84aef0 100644
--- a/lib/js/src/thrift.js
+++ b/lib/js/src/thrift.js
@@ -1084,7 +1084,7 @@
         this.rstack = [];
         this.rpos = [];
 
-        received = this.transport.readAll();
+        var received = this.transport.readAll();
 
         if (typeof JSONInt64 !== 'undefined' && typeof JSONInt64.parse === 'function') {
             this.robj = JSONInt64.parse(received);