title: I meet a problem when I use websocket in my vue project
body: <p>Wrong when using websocket, &quot;Uncaught TypeError: Cannot read property 'subscribe' of undefined&quot;
  <br></p>
  <p><img src="https://i.stack.imgur.com/6H202.png" alt="enter image description here" /></p>
  <p>My code is :</p>
  <pre><code>    init() {
                  let socket = new SockJS('http://127.0.0.1:8080/gs-guide-websocket');
                  this.stompClient = Stomp.over(socket);
                  this.stompClient.connect({}, function (frame) {
                      this.stompClient.subscribe('/topic/greetings', function (msg) {
                          console.log(msg.body)
                      });
                  });
              },
  </code></pre>