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WebSocket Logger

Log all the communication of every WebSocket

// ==UserScript==
// @name        WebSocket Logger
// @namespace   esterTion
// @description Log all the communication of every WebSocket
// @include     *://*/*
// @version     2
// @grant       none
// @run-at      document-start
// ==/UserScript==

var scriptString = (function () {
  if (window.Proxy == undefined) return;
  var oldWS = window.WebSocket;
  var loggerIncrement = 1;
  function processDataForOutput(data) {
    if (typeof data == 'string') return data;
    else if (data.byteLength != undefined) {
      var val = { orig: data, uintarr: new Uint8Array(data) };
      var arr = [], i = 0;
      for (; i < data.byteLength; i++) {
        arr.push(val.uintarr[i]);
      }
      var hexarr = arr.map(function (i) { var s = i.toString(16); while (s.length < 2) s = '0' + s; return s; });
      val.hexstr = hexarr.join('');
      val.string = unescape(hexarr.map(function (i) { return '%' + i; }).join(''));
      val.b64str = btoa(val.string);
      try {
        val.string = decodeURIComponent(escape(val.string));
      } catch (e) { }
      return val;
    }
  }
  var proxyDesc = {
    set: function (target, prop, val) {
      if (prop == 'onmessage') {
        var oldMessage = val;
        val = function (e) {
          console.log(`#${target.WSLoggerId} Msg from server << `, processDataForOutput(e.data));
          oldMessage(e);
        };
      }
      return target[prop] = val;
    },
    get: function (target, prop) {
      var val = target[prop];
      if (prop == 'send') val = function (data) {
        console.log(`#${target.WSLoggerId} Msg from client >> `, processDataForOutput(data));
        target.send(data);
      };
      else if (typeof val == 'function') val = val.bind(target);
      return val;
    }
  };
  WebSocket = new Proxy(oldWS, {
    construct: function (target, args, newTarget) {
      var obj = new target(args[0]);
      obj.WSLoggerId = loggerIncrement++;
      console.log(`WebSocket #${obj.WSLoggerId} created, connecting to`, args[0]);
      return new Proxy(obj, proxyDesc);
    }
  });
});

var observer = new MutationObserver(function () {
  if (document.head) {
    observer.disconnect();
    var script = document.createElement('script');
    script.innerHTML = '(' + scriptString + ')();';
    document.head.appendChild(script);
    script.remove();
  }
});
observer.observe(document, { subtree: true, childList: true });