[Javascript] Replace/modify javascript functions at runtime?

[Håkan Magnusson]

Note, this only has to work in Mozilla as of now. Let me illustrate an 
example.

------ text.js:

function Plus(iArg1, iArg2) {
	return (sArg1 + iArg2);
}

/------ text.js:

Now if I check 'window.Plus' i find the string (representation?) 
"function Plus(iArg1, iArg2) {	return (sArg1 + iArg2);}". All good and 
well. Now I want to add one line of code in this function, at runtime.

sNewFunc = window.Plus.toString().replace('{', '{ MyFunction();');

and sNewFunc now displays:
"function Plus(iArg1, iArg2) { MyFunction();	return (sArg1 + iArg2);}"

Then I'm doing the following (I think this is where I do it wrong):

window.Plus = sNewFunc;

This "works", in that it doesn't generate any errors. When I check 
window.Plus again, my "new" function is returned. When I run the 
window.Plus function, however, it seems that the browser is still using 
the "old" function.

If what I'm trying to do is possible, it would be VERY cool, and I'm not 
afraid of complex solutions, as long as they are managable. I had an 
idea of creating a whole new "container" (documentFragment?) for my 
"rewritten" functions, but err...

Håkan