var key, x, y, z;
// impure
key = 1;
var { [key++]: y, ...x } = { 1: 1, a: 1 };
expect(x).toEqual({ a: 1 });
expect(key).toBe(2);
expect(1).toBe(y);

// takes care of the order

key = 1;
var { [++key]: y, [++key]: z, ...rest} = {2: 2, 3: 3};
expect(y).toBe(2);
expect(z).toBe(3);

// pure, computed property should remain as-is
key = 2;
({ [key]: y, z, ...x } = {2: "two", z: "zee"});
expect(y).toBe("two");
expect(x).toEqual({});
expect(z).toBe("zee");