Destructuring.

destructuring.js

var [first, second, ...rest] = [1, 2, 3, 4, 5]; 

console.log('first =', first);
console.log('second =', second);
console.log('rest =', rest);
// => first = 1
// => second = 2
// => rest = [3, 4, 5]

function printPoint({x: x, y: y}) {
  console.log('x = %d, y = %d', x, y); 
}

printPoint({x: 2, y: 3});
// => x = 2, y = 3

function addPoints ([x1, y1], [x2, y2]) {
  return [x1 + x2, y1 + y2];
}

console.log('addPoints([1, 2], [3, 4]) =', addPoints([1, 2], [3, 4]));
// => addPoints([1, 2], [3, 4]) = [4, 6]