ws-monkey-patch.js

WebSocket.prototype.oldSendImpl = WebSocket.prototype.send;

WebSocket.prototype.send =
  function (data) {
    console.log("\u2192 " + data);
    this.oldSendImpl(data);
    this.addEventListener(
      "message",
      function (msg) {
        console.log("\u2190 " + msg.data);
      },
      false
    );
    this.send =
      function (data) {
        this.oldSendImpl(data);
        console.log("\u2192 " + data);
      };
  };

Don’t use this in a production environment… ☺