as noted by mscdex: openBox should use the emptyFn variable instead of creating a new empty function every time when readonly and cb are undefined.

imap.js

@@ -404,7 +404,7 @@ ImapConnection.prototype.openBox = function(name, readOnly, cb) {
     this._resetBox();
   if (typeof cb === 'undefined') {
     if(typeof readOnly === 'undefined') {
-      cb = function(){};
+      cb = emptyFn;
     } else {
       cb = readOnly;
     }
@@ -1418,4 +1418,4 @@ function pipe(pair, socket) {
   socket.on('close', onclose);
 
   return cleartext;
-}
+}