the other benefit is that `void 0` cannot be overwritten in sloppy mode, whereas you can do something crazy like this:

    undefined = 'lol';

No you can't. You can do something like function(undefined) {}, but the global 'undefined' is non-writable and non-configurable.

That's an ES5 change. With ES3, you can overwrite NaN, Infinity, and undefined.

Only in strict mode I though no ?

Generally. Technically, it's a "breaking change".

As you can imagine, this didn't actually affect anyone.