Javascript - Replacing the escape character in a string literal

I am trying to replace the backslash (escape) character in a Javascript string literal.

I need to replace it with a double backslash so that I can then do a redirect:

var newpath = 'file:///C:\funstuff\buildtools\viewer.html'.replace(/\\/g,"\\");
window.location = newpath;

However, it seems to have no result.

I don't have the option of properly escaping the backslashes before they are handled by Javascript.

How can I replace (\) with (\\) so that Javascript will be happy?

Thanks, Derek