Echo JS 0.11.0

Notice that `x === void 0` is not always as same as `typeof x === 'undefined'` in browser context:

console.log(document.all === void 0); // false
console.log(document.all === null); // false
console.log(document.all == void 0); // true
console.log(typeof document.all); // 'undefined'

But it does not mean anyone of them is incorrect, since there is no defined behavior for such a monster thing in ECMAScript.

It's just that `document.all` is a strange and obscure beast. It's a legacy "host" object of the days of Internet Explorer 4 or so.

Omg, this looks awful.

Thanks for pointing it out!