How to fast the data transfer rate with WebSocket module 'ws' in Espruino?

test code with no btoa(), and interval = 0

function onInit(){
  var ssid = "HGiga3";
  var wifiOpts = {password:"20071203"};
  var wifi = require("Wifi");

  wifi.connect(ssid, wifiOpts, function(err){
    console.log("connected? err=", err, "info=", wifi.getIP());
    var WebSocket = require("ws");
    var host = "192.168.1.9";
    var ws = new WebSocket(host,{
      path: '/',
      port: 5004, // default is 80
      protocolVersion: 13, // websocket protocol version, default is 13
      origin: 'Espruino',
      keepAlive: 60,
    });

    ws.on('open', function() {
      console.log("connected");
      //ws.send('hello, server');
      var packet = "12345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890";
      var pktNum = 0;
      var ta = 0;
      var id = setInterval(function(){
        var t1 = getTime();
        ws.send(packet);
        pktNum ++;
        console.log("Packet NO.: " + pktNum + ", time used: " + (t2 = getTime() - t1) + "s");
        ta += t2;
        if(pktNum >=101){
          console.log("total time used: " + ta +"s");
          clearInterval(id);
        }
      }, 0);
    });
  });
}

result:

connected? err= null info= {
  "ip": "192.168.1.30",
  "netmask": "255.255.255.0",
  "gw": "192.168.1.1",
  "mac": "30:ae:a4:03:96:a8"
 }
connected
Packet NO.: 1, time used: 0.635692s
Packet NO.: 2, time used: 0.643326s
Packet NO.: 3, time used: 0.639247s
Packet NO.: 4, time used: 0.637486s
Packet NO.: 5, time used: 0.638007s
Packet NO.: 6, time used: 0.639673s
Packet NO.: 7, time used: 0.635873s
Packet NO.: 8, time used: 0.639083s
Packet NO.: 9, time used: 0.638372s
Packet NO.: 10, time used: 0.635825s
Packet NO.: 11, time used: 0.63933s
Packet NO.: 12, time used: 0.640514s
Packet NO.: 13, time used: 0.651622s
Packet NO.: 14, time used: 0.635399s
Packet NO.: 15, time used: 0.633999s
Packet NO.: 16, time used: 0.642046s
Packet NO.: 17, time used: 0.636034s
Packet NO.: 18, time used: 0.634s
Packet NO.: 19, time used: 0.641917s
Packet NO.: 20, time used: 0.634763s
Packet NO.: 21, time used: 0.637004s
Packet NO.: 22, time used: 0.639767s
Packet NO.: 23, time used: 0.640957s
Packet NO.: 24, time used: 0.641996s
Packet NO.: 25, time used: 0.641126s
Packet NO.: 26, time used: 0.63957s
Packet NO.: 27, time used: 0.641609s
Packet NO.: 28, time used: 0.637018s
Packet NO.: 29, time used: 0.6368s
Packet NO.: 30, time used: 0.634749s
Packet NO.: 31, time used: 0.633586s
Packet NO.: 32, time used: 0.634311s
Packet NO.: 33, time used: 0.63496s
Packet NO.: 34, time used: 0.640297s
Packet NO.: 35, time used: 0.64408s
Packet NO.: 36, time used: 0.63855s
Packet NO.: 37, time used: 0.632856s
Packet NO.: 38, time used: 0.639827s
Packet NO.: 39, time used: 0.641707s
Packet NO.: 40, time used: 0.635856s
Packet NO.: 41, time used: 0.638333s
Packet NO.: 42, time used: 0.641669s
Packet NO.: 43, time used: 0.634372s
Packet NO.: 44, time used: 0.65415s
Packet NO.: 45, time used: 0.639517s
Packet NO.: 46, time used: 0.637973s
Packet NO.: 47, time used: 0.644115s
Packet NO.: 48, time used: 0.638485s
Packet NO.: 49, time used: 0.642308s
Packet NO.: 50, time used: 0.639105s
Packet NO.: 51, time used: 0.636765s
Packet NO.: 52, time used: 0.631903s
Packet NO.: 53, time used: 0.681386s
Packet NO.: 54, time used: 0.634737s
Packet NO.: 55, time used: 0.641648s
Packet NO.: 56, time used: 0.643582s
Packet NO.: 57, time used: 0.636885s
Packet NO.: 58, time used: 0.631757s
Packet NO.: 59, time used: 0.642512s
Packet NO.: 60, time used: 0.639893s
Packet NO.: 61, time used: 0.638397s
Packet NO.: 62, time used: 0.63751s
Packet NO.: 63, time used: 0.641528s
Packet NO.: 64, time used: 0.639858s
Packet NO.: 65, time used: 0.642329s
Packet NO.: 66, time used: 0.636603s
Packet NO.: 67, time used: 0.634986s
Packet NO.: 68, time used: 0.641883s
Packet NO.: 69, time used: 0.637135s
Packet NO.: 70, time used: 0.639046s
Packet NO.: 71, time used: 0.641357s
Packet NO.: 72, time used: 0.633942s
Packet NO.: 73, time used: 0.634675s
Packet NO.: 74, time used: 0.642398s
Packet NO.: 75, time used: 0.650468s
Packet NO.: 76, time used: 0.638624s
Packet NO.: 77, time used: 0.643335s
Packet NO.: 78, time used: 0.637059s
Packet NO.: 79, time used: 0.635053s
Packet NO.: 80, time used: 0.637182s
Packet NO.: 81, time used: 0.638033s
Packet NO.: 82, time used: 0.635974s
Packet NO.: 83, time used: 0.638443s
Packet NO.: 84, time used: 0.63591s
Packet NO.: 85, time used: 0.639598s
Packet NO.: 86, time used: 0.639959s
Packet NO.: 87, time used: 0.637911s
Packet NO.: 88, time used: 0.638151s
Packet NO.: 89, time used: 0.636811s
Packet NO.: 90, time used: 0.636061s
Packet NO.: 91, time used: 0.636077s
Packet NO.: 92, time used: 0.637843s
Packet NO.: 93, time used: 0.641588s
Packet NO.: 94, time used: 0.639297s
Packet NO.: 95, time used: 0.642088s
Packet NO.: 96, time used: 0.635662s
Packet NO.: 97, time used: 0.638305s
Packet NO.: 98, time used: 0.634205s
Packet NO.: 99, time used: 0.644576s
Packet NO.: 100, time used: 0.644314s
Packet NO.: 101, time used: 0.639154s
total time used: 64.56325700000s

with no btoa(), about 200ms is saved per 230 bytes packet.