gistfile1.js

// A listener is added in rule-view.js:
this.valueSpan.addEventListener("click", (event) => {
  let target = event.target;

  if (target.nodeName === "a") {
    event.stopPropagation();
    event.preventDefault();
    this.browserWindow.openUILinkIn(target.href, "tab");
  }
}, false);

// Then we try to get the event listeners:
getEventListeners: function(node) {
  let global = node.ownerGlobal ? node.ownerGlobal.wrappedJSObject : node.wrappedJSObject;

  let dbg = new Debugger();
  let globalDebugObject = dbg.addDebuggee(global);
  let handlers = eventListenerService.getListenerInfoFor(node);
 
  for (let handler of handlers) {
    let listener = handler.listenerObject;
 
    if (listener) {
      let listenerDebugObject = globalDebugObject.makeDebuggeeValue(listener);
      let script = listenerDebugObject.script;

      // script is undefined for some XUL listeners in the browser debugger... why?