Turning on `debug` causes uglify to swap the first entry in its nodes from a string to a `NodeWithToken` object. If you look in `parse-js.js` I have modified the NodeWithToken object to behave as much as possible like a string, since existing code is likely to be written with that assumption in mind. However, `typeof` checks are impossible to fool, so I had to modify this one. `typeof subnode.valueOf()` will return the same result as `typeof subnode` as long as subnode is non-null and not `undefined`, so this should be a safe change to make.