I'm working on a FireFox extension that listens to onStateChange. When the current document has been loaded it should insert a script to the page and it should be able to call the script on a button event.

Now I am able to add a button to all webpages by using:

nsCOMPtr<nsIDOMElement> NewInputElementTest;
rv = htmlDoc->CreateElement(NS_LITERAL_STRING("input"),getter_AddRefs(NewInputElementTest));

rv = NewInputElementTest->SetAttribute(NS_LITERAL_STRING("type"),NS_LITERAL_STRING("button"));

rv = NewInputElementTest->SetAttribute(NS_LITERAL_STRING("value"),NS_LITERAL_STRING("hummer"));

rv = body->AppendChild(NewInputElementTest,getter_AddRefs(AddedNewInputElement2));

The button is displayed correctly.


I wish to use the same procedure to add a SCRIPT to the page, like so:

rv = htmlDoc->CreateElement(NS_LITERAL_STRING("script"),getter_AddRefs(NewInputElement));
rv = NewInputElement->SetAttribute(NS_LITERAL_STRING("type"),NS_LITERAL_STRING("text/javascript"));
rv = NewInputElement->SetAttribute(NS_LITERAL_STRING("text"),NS_LITERAL_STRING("alert('hello world!')"));
rv = body->AppendChild(NewInputElement,getter_AddRefs(AddedNewInputElement));

All functions return success, but no script is added to the page. No alert is displayed, and if i insert a function and call it from the button.onclick then the FireFox log displayes that the function is not available.

If I use the exact same procedure from a javascript inside the html page, then it works find and the alert pops up.

Do I need to do anything to enable the script from my extension or why is the script not available from the button or anywhere else?

I'm working on a FireFox extension that listens to onStateChange. When the current document has been loaded it should insert a script to the page and it should be able to call the script on a button event.

Now I am able to add a button to all webpages by using:

nsCOMPtr<nsIDOMElement> NewInputElementTest;
rv = htmlDoc->CreateElement(NS_LITERAL_STRING("input"),getter_AddRefs(NewInputElementTest));

rv = NewInputElementTest->SetAttribute(NS_LITERAL_STRING("type"),NS_LITERAL_STRING("button"));

rv = NewInputElementTest->SetAttribute(NS_LITERAL_STRING("value"),NS_LITERAL_STRING("hummer"));

rv = body->AppendChild(NewInputElementTest,getter_AddRefs(AddedNewInputElement2));

The button is displayed correctly.


I wish to use the same procedure to add a SCRIPT to the page, like so:

rv = htmlDoc->CreateElement(NS_LITERAL_STRING("script"),getter_AddRefs(NewInputElement));
rv = NewInputElement->SetAttribute(NS_LITERAL_STRING("type"),NS_LITERAL_STRING("text/javascript"));
rv = NewInputElement->SetAttribute(NS_LITERAL_STRING("text"),NS_LITERAL_STRING("alert('hello world!')"));
rv = body->AppendChild(NewInputElement,getter_AddRefs(AddedNewInputElement));

All functions return success, but no script is added to the page. No alert is displayed, and if i insert a function and call it from the button.onclick then the FireFox log displayes that the function is not available.

If I use the exact same procedure from a javascript inside the html page, then it works find and the alert pops up.

Do I need to do anything to enable the script from my extension or why is the script not available from the button or anywhere else?

• javascript
• firefox-addon

• possible duplicate of How to inject javascript into page, from a Firefox add-on, and run it? – user2284570 Commented Nov 9, 2014 at 23:14

2 Answers 2

I hate to say it after you created a bunch of code, but check out Greasemonkey: https://addons.mozilla/en-US/firefox/addon/748

It'll probably handle a lot of your work for you.

Yes, sounds like you're tryin to re-invent the wheel. Use Greasemonkey as Oren suggested.

Here is a Greasemonkey script that I use to load external JS framework (Prototype and Scriptaculous in this case) load any number of external files (js and css) into a page.

// ==UserScript==
// @name           External Loader
// @namespace      http://ifelse
// @description    Loads external JS and CSS
// @include        http://*.yoursitedomainetc./*
// ==/UserScript==

var hasPrototype  = ('Prototype' in unsafeWindow);
var hasEffects    = ('Effect'    in unsafeWindow);

function _require(url, isCSS) {
    if (isCSS) {
        var script = document.createElement('link');
        script.setAttribute('type', 'text/css');
        script.setAttribute('rel',  'stylesheet');
        script.setAttribute('href', url);
    } else {
        var script = document.createElement('script');
        script.setAttribute('type',    'text/javascript');
        script.setAttribute('charset', 'UTF-8');
        script.src = url;
    }
    document.getElementsByTagName('head')[0].appendChild(script);
}

//  Load prototype; shouldn't get here because it is already on the page
if ( !hasPrototype ) {
    _require('http://path./to/prototype/1.6.0.2/prototype.js');
}

//  Load scriptaculous effects if it's not already loaded
if ( !hasEffects ) {
    _require('http://path./to/scriptaculous/1.8.1/effects.js');
}

//  Add greasemonkey ajax object
//  Copies format of Prototype Ajax.Request to
//  Allow to easily swap out at a later point (i.e. no longer FF plugin)
unsafeWindow.Remote = new Object;
unsafeWindow.Remote.Ajax = function(url, options) {
    if (options.onCreate) {
        options["onCreate"]();
    }

    var request = {
        method: options.method || 'get',
        url: url + ('?' + unsafeWindow.Object.toQueryString(options.parameters) || ''),
        onload: function(response) {
            if (response.status == 200)
            options["onComplete"](response);
            options["onSuccess"]();
        },
        onerror: options.onFailure || null
    };
    window.setTimeout(GM_xmlhttpRequest, 0, request);
};

//  Load these External files
_require('http://path/to/anything/and/dont/cache/it.js' + '?cache=' + (new Date()).getTime());
_require('http://paht/to/something/else.css', true);
}