echo-client.js

      var websocket = new WebSocket('ws://echo.websocket.org/');

      websocket.onopen = function(e) {
        console.log('socket open');
      }

      websocket.onmessage = function (e){
        console.log(e.data)
      };

      websocket.onclose = function(e){
        console.log('connection closed')
      };

      window.setInterval(function(){
        websocket.send('ping');
      }, 1000);