Which one of these two ways is faster and why?
window.setTimeout("func()", 100);
Or
window.setTimeout(function(){func();}, 100);
I'm guessing the second way is faster if for no other reason other than John Resig and all the ninjas use it, I'm guessing because it already parsed as opposed to the first way which it would have to create a new parsing "thingie". I vaguely recall this being one of the reasons people don't like eval().
Also while I have you here, in the second code snipplet, is the first semi-colon considered good practice in such a case?
There's a third faster/simpler option:
window.setTimeout(func, 100);
...strictly relating to your question, the second is faster, as it's still a reference - not an evaluation, which is always fairly expensive. As for the semicolon, yes it's a good practice to always use them. They should never have been optional in my opinion, but plenty will disagree with me here. You can't really argue against being explicit in your code, that's always a good thing.