Detect when page loaded with firefox extension

Question

How to detect when a page is loaded (in any tab) with a firefox extension (automatically, no start-button or anything) (and display an alert message for example) ?

Answer 1

https://developer.mozilla.org/en/Code_snippets/On_page_load

Dont miss this part: "

Current Firefox trunk nightlies will fire the onPageLoad function for not only documents, but xul:images (favicons in tabbrowser). If you only want to handle documents, ensure aEvent.originalTarget.nodeName == "#document" [1].

"

Answer 2

function startup() {

mainWindow = window.QueryInterface(Components.interfaces.nsIInterfaceRequestor)
                         .getInterface(Components.interfaces.nsIWebNavigation)
                         .QueryInterface(Components.interfaces.nsIDocShellTreeItem)
                         .rootTreeItem
                         .QueryInterface(Components.interfaces.nsIInterfaceRequestor)
                         .getInterface(Components.interfaces.nsIDOMWindow); 

    mainWindow.getBrowser().addEventListener("load", listener, false);


    // Sidebar is loaded and mainwindow is ready                   
    }

    var listener = function(e){
        alert("Hai");
        //To remove event listener
        //mainWindow.getBrowser().removeEventListener("load",listener, false);
    }  


window.addEventListener("load", startup, false);

This is code is enough for this purpose.

Though this is late, I'm answering this question to minimize the search time.