[perf] Use shared instance of the encoder (socketio#2825)

lib/client.js

@@ -13,6 +13,12 @@ var url = require('url');
 
 module.exports = Client;
 
+/**
+ * Packet encoder
+ */
+
+var encoder = new parser.Encoder();
+
 /**
  * Client constructor.
  *
@@ -24,7 +30,6 @@ module.exports = Client;
 function Client(server, conn){
   this.server = server;
   this.conn = conn;
-  this.encoder = new parser.Encoder();
   this.decoder = new parser.Decoder();
   this.id = conn.id;
   this.request = conn.request;
@@ -153,9 +158,7 @@ Client.prototype.packet = function(packet, opts){
   if ('open' == this.conn.readyState) {
     debug('writing packet %j', packet);
     if (!opts.preEncoded) { // not broadcasting, need to encode
-      this.encoder.encode(packet, function (encodedPackets) { // encode, then write results to engine
-        writeToEngine(encodedPackets);
-      });
+      encoder.encode(packet, writeToEngine); // encode, then write results to engine
     } else { // a broadcast pre-encodes a packet
       writeToEngine(packet);
     }