It's actually not that new since it's been there since Firefox 2.0, but pretty cool anyway. JavaScript has borrowed some nice features of Python, namely generators and multiple-value returns.
The classical Fibonacci suite written with JavaScript generators:
function fib() {
var i = 0, j = 1;
while (true) {
yield i;
[i, j] = [j, i + j];
}
}
var g = fib();
for (let i = 0; i < 10; i++)
print(g.next());
The multiple-value returns is actually a subset of the more general destructuring assignment which I find a bit too-much, since taken to the extreme it actually makes the code less readable... unless you have some experience with Prolog unification :-)
Anyway, it's nice to see JavaScript evolve. IE won't have it for the 5 (or more) years to come though...