As someone else also mentioned in the comments, it is unapologetically dynamic. In many ways, this reminds me of Perl. The array destructuring assignment is such a common pattern in that language (eg. http://perldoc.perl.org/functions/caller.html)
What's even more exciting/terrifying is that ES6 goes even beyond the patterns allowed in Perl!
ES6:
let [,,,,,,,,, tenth_item] = somearray;
my (undef x 9, $tenth_item) = @somearray;
This is not only better because now there is a visible thing to see and talk about, but also allows the comma operator to be much less restricted and frees the programmer to be more expressive. In Perl, multiple commas are collapsed similar like multiple whitespace collapses in HTML. The expression a,,,,,,b is identical to a,b – also it does not matter where in the expression the multiple commas are.
In ES5 and later multiple commas at the end are collapsed into one, but otherwise multiple commas are kept. This is lame because inconsistent.
let [tenth_item] = somearray.slice(9) let [,second,,fourth,,sixth]