How to get the html source code

Hi every one,

i'm trying to get the html's source code when the browser load
completed;

now i exec this script to that;

"(function(){return document.documentElement.innerHTML})();"

how can i use xpcom api to do this?

there is another question is "how can i use jscript to invock c++
function from html page?"

Could you help me ?

Thank's

alvin