I use similar approach, and yes, it works fine as long as spammers don't figure how to extract your email address from JavaScript code.

function em(e2, e1) { return 'mailto:' + e1 + '@' + e2 + '.com'; }

... and somewhere in your HTML code:

onClick="this.href=em('foobar', 'contact')"

The name of the function may be more cryptic and I just thought it may be even dynamic (random), as well as the order of arguments.

Right, great solution until people start using it. Then it will be trivial to add this feature to spam bots. I bet some already figured it out. It's not that hard to integrate a Javascript VM.

I was going to ask, "What about those without JavaScript or that have it disabled?" but who cares about them. 99% of the world has JavaScript probably!

Doesn't this defeat the main purpose, though? At least on that page, the fall-back was just in the mail[aht]whatever format, which I suspect spammers have learned to decipher long ago.

I wondered that too. But apparently not, because we've got the proof: our spam has gone way down. Though if it goes up again I'll bot-proof that fall-back page a bit more.