core: object/array destructuring assignment.

[drsm]

> var [a, b, ...c] = [1,2,3,4]
undefined
> [a,b,c]
[ 1, 2, [ 3, 4 ] ]
> var { 1:x, 2:y, length } = [1,2,3,4]
undefined
> [x,y, length]
[ 2, 3, 4 ]
> var { x, ...xs } = { x: 2, x1: 1, x0: 0}
undefined
> [x, xs]
[ 2, { x1: 1, x0: 0 } ]

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Destructuring_assignment