Search Support

Avoid support scams. We will never ask you to call or text a phone number or share personal information. Please report suspicious activity using the “Report Abuse” option.

Learn More

Lolu chungechunge lwabekwa kunqolobane. Uyacelwa ubuze umbuzo omusha uma udinga usizo.

JavaScript in firefox.cfg can't access `document`

  • 3 uphendule
  • 0 zinale nkinga
  • 110 views
  • Igcine ukuphendulwa ngu jazali

more options

As I understand, `autoconfig.js` (with `firefox.cfg`) can be used to have JavaScript run during startup to control Firefox's UI elements.

I have set up `autoconfig.js` in my `/usr/lib/firefox-developer-edition/defaults/pref` folder (I'm on EndeavourOS Linux). As instructed here, I've already put the two required files, `autoconfig.js` and `firefox.cfg` in their correct folders (`/usr/lib/firefox-developer-edition/defaults/pref` and `/usr/lib/firefox-developer-edition` in my machine).

The file `firefox.cfg` contains the following code:

 //
 (() => {
   var tabbar = document.getElementById("TabsToolbar");
 })();


However, every time I run Firefox, this message will appear:

 "Failed to read the configuration file. Please contact your system administrator."


If I empty out the `firefox.cfg` file, Firefox will run normally without showing the error message. It will also run normally if I just have something like this in the file:

 //
 (() => {
   var testVar = "";
 })();


I don't understand why the JavaScript code can't access the Firefox UI elements through `document` or `window.document`. If `autoconfig.js` isn't build for that, what should I use to change my browser's UI elements through JavaScript?

Thank you.

As I understand, `autoconfig.js` (with `firefox.cfg`) can be used to have JavaScript run during startup to control Firefox's UI elements. I have set up `autoconfig.js` in my `/usr/lib/firefox-developer-edition/defaults/pref` folder (I'm on EndeavourOS Linux). As instructed [https://support.mozilla.org/en-US/kb/customizing-firefox-using-autoconfig here], I've already put the two required files, `autoconfig.js` and `firefox.cfg` in their correct folders (`/usr/lib/firefox-developer-edition/defaults/pref` and `/usr/lib/firefox-developer-edition` in my machine). The file `firefox.cfg` contains the following code: // (() => { var tabbar = document.getElementById("TabsToolbar"); })(); However, every time I run Firefox, this message will appear: "Failed to read the configuration file. Please contact your system administrator." If I empty out the `firefox.cfg` file, Firefox will run normally without showing the error message. It will also run normally if I just have something like this in the file: // (() => { var testVar = ""; })(); I don't understand why the JavaScript code can't access the Firefox UI elements through `document` or `window.document`. If `autoconfig.js` isn't build for that, what should I use to change my browser's UI elements through JavaScript? Thank you.
Ama-screenshot ananyekiwe

Okulungisiwe ngu jazali

Isisombululo esikhethiwe

Note that you need a lot more code to be able to access a browser window (i.e. add an observer that is triggered when you open a window).


// start autoconfig.cfg with a comment line
try {
 function ConfigJS() { Services.obs.addObserver(this, 'chrome-document-global-created', false); }
 ConfigJS.prototype = {
  observe: function (aSubject) { aSubject.addEventListener('DOMContentLoaded', this, {once: true}); },
  handleEvent: function (aEvent) {
   let document = aEvent.originalTarget;
   let window = document.defaultView;
   let location = window.location;

   if (/^(chrome:(?!\/\/(global\/content\/commonDialog|browser\/content\/webext-panels)\.x?html)|about:(?!blank))/i.test(location.href)) {
    if (window._gBrowser) { //place your code here
       var tabbar = window.document.getElementById("TabsToolbar");
    }  // gBrowser
   }   // location
  }    // handleEvent
 };    // prototype
 if (!Services.appinfo.inSafeMode) { new ConfigJS(); }
} catch(e) {Cu.reportError(e);}

Funda le mpendulo ngokuhambisana nalesi sihloko 👍 0

All Replies (3)

more options

Did you disable the sandbox via autoconfig.js ?

Content of autoconfig.js:

//start autoconfig.js with a comment line
pref("general.config.filename", "autoconfig.cfg");
pref("general.config.obscure_value", 0);
pref("general.config.sandbox_enabled", false);
more options

Isisombululo Esikhethiwe

Note that you need a lot more code to be able to access a browser window (i.e. add an observer that is triggered when you open a window).


// start autoconfig.cfg with a comment line
try {
 function ConfigJS() { Services.obs.addObserver(this, 'chrome-document-global-created', false); }
 ConfigJS.prototype = {
  observe: function (aSubject) { aSubject.addEventListener('DOMContentLoaded', this, {once: true}); },
  handleEvent: function (aEvent) {
   let document = aEvent.originalTarget;
   let window = document.defaultView;
   let location = window.location;

   if (/^(chrome:(?!\/\/(global\/content\/commonDialog|browser\/content\/webext-panels)\.x?html)|about:(?!blank))/i.test(location.href)) {
    if (window._gBrowser) { //place your code here
       var tabbar = window.document.getElementById("TabsToolbar");
    }  // gBrowser
   }   // location
  }    // handleEvent
 };    // prototype
 if (!Services.appinfo.inSafeMode) { new ConfigJS(); }
} catch(e) {Cu.reportError(e);}

more options

Hi. Thank you very much for the answer! My script can now access `document` thanks to your code. But I'm still confused on how to implement the following into the snipped you provided:

 var tabbar = window.document.getElementById("TabsToolbar");
 function showHideTabbar() {
   var sidebarBox = window.document.getElementById("sidebar-box");
   var sidebarTST = sidebarBox.getAttribute("sidebarcommand");
   if (!sidebarBox.hidden && sidebarTST === "treestyletab_piro_sakura_ne_jp-sidebar-action") {
     tabbar.style.visibility = "collapse";
   }
   else {
     tabbar.style.visibility = "visible";
   }
 }
 var observer = new MutationObserver(showHideTabbar);
 observer.observe(window.document.getElementById("sidebar-box"), { attributes: true, attributeFilter: ["sidebarcommand", "hidden"] });


Its purpose is to hide the tab strip on top when Tree Style Tab is open on the sidebar.

I found that it worked when I ran it through the Browser Toolbox. But it had no effect when I put it into the `if (window._gBrowser) {}` scope. I'm not too familiar with JavaScript, so I can't quite figure out what's wrong.

Okulungisiwe ngu jazali