var init = function() {

  var log = function(str) {

    $("#log").append(str);

    $("#log").append("\n");

  };

  var init_extension = function() {

    // when activated, my extension tries to use addEventListener to intercept the form submission

    var form_submitted = function(event) {

      log("Submitted the form! (addEventListener handler)");

    };

​

    log("setting extension handlers!");

    var forms = document.querySelectorAll("form");

    for (i=0; i<forms.length; i++) {

      forms[i].addEventListener("submit", form_submitted, false);

    }

    // hijack jQuery event handlers if present

    if ($ !== undefined && $.event !== undefined && $.event.trigger !== undefined) {

      var orig_handler = $.event.trigger;

      var new_handler = function(event, data, elem) {

        var type = event.type || event;

        var eventObj = new Event(type);

​

        elem.dispatchEvent(eventObj);

        log("Event type: " + String(type));

        return orig_handler.apply(event, arguments);

      };

      $.event.trigger = new_handler;

    }

​

  };

​

  log("Init");

​

  // the page's submission handler calls stopPropagation & preventDefault before returning false

  var ajaxSubmit = function(event) {

    log(event);

    event.stopPropagation();

    event.preventDefault();

    log("Submitted the form! (jQuery delegate handler)");

    return false;

  };

  // the page's JavaScript sets a handler with delegate next:

  $("body").delegate('form', "submit", $.proxy(ajaxSubmit, this));

  // and then overrides the behavior of the submit button to trigger "submit" on the form via jQuery

  $("body").delegate("#submit", "click", function(a){

    $(this.form).trigger("submit", {

      target: a.target

    });

    return false;

  });

 document.querySelector("#activate_extension").addEventListener("click", init_extension);

}();