如何从Firefox扩展名执行网页名称空间（范围）中的javascript代码？

Question

I'm looking for a clean way to call/execute/redefine javascript code from a webpage, within firefox, through a firefox extension. My temporary solution is to use the scratchpad (Shift-F4, Ctrl-A, Ctrl-V, Ctrl-R), it works fine but is a sad work-around. Greasemonkey would be my last resort, very very last.

Here' the code so far:

main.js:

exports.main = function() {
  var data = require("self").data;
  var pageMod = require("page-mod");
  pageMod.PageMod({
    include: "*.google.com",
    contentScriptFile: data.url("my-script.js")
  });
};

my-script.js

$('#mydiv').html('yo')
alreadyHere.sayHello=function (){alert('Bonjour');}

This code halts on line #1 of my-script.js saying that $ is not defined. Problem of namespace/scope.

How can I work within the namespace/scope of the webpage, from my extension, like I do with the scratchpad?

Edit: There should be a link between window.content of the firefox main window and alreadyHere.sayHello from the webpage, no?

window.content.(things).alreadyHere.sayHello();

What am I missing here?

Answer 1

HELL YEAH.

window.content.document.defaultView.wrappedJSObject.$('#mydiv').html('yo')
window.content.document.defaultView.wrappedJSObject.alreadyHere.sayHello();

Thanks Mridang Agarwalla here

Answer 2

Did you tried in Firebug console?

And also,

Make sure you code is within

$(document).ready(function () {
  //your code here
});

and most important jQuery is properly loaded