[shardling]

Yeah, you could test this in the first example by replacing the string 'interval' with something like "alert(str.length)", and then redefining console.log=eval.

e: nm, I missed pcwalton's point -- when you call eval indirectly it isn't accessing the same scope. So redefining console.log couldn't access local variables like str. (I don't think?)

[masklinn]

Correct. Not only is eval not a good idea in general, but it's a very weird beast in javascript. See http://perfectionkills.com/global-eval-what-are-the-options/ for a very complete exposition of its weirdness.