JS destructuring assignment syntax

destructuring.js

// see: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Destructuring_assignment
// see: https://hacks.mozilla.org/2015/05/es6-in-depth-destructuring/
var a, b, c, x, y, z, key, foo, bar, baz;

// destructuring arrays (and default values)
[a, b, c=5] = [10, 20];
a // 10
b // 20
c // 5

// swapping variable values
[a, b] = [a, b]
a // 20
b // 10

// ignoring vars
var [a, , b] = [1, 2, 3];
a // 1
b // 3

// remainder of array
var [a, ...b] = [1, 2, 3];
a // 1
b // [2, 3]

// destructuring nested arrays
[foo, [[bar], baz]] = [1, [[2], 3]]
foo // 1
bar // 2
baz // 3

// destructuring arrays in method params
atest = ([a, ...rest] = []) => rest
atest([1, 2]) // [2]

// destructuring objects (and default values)
{ x=5, y } = { y: 7 };
x // 5
y // 7

// remainder of object
{ a, ...b } = { b: 7 } // may need to be put in parenthases: ({ a, ...b } = { b: 7 })
a // undefined
b // { b: 7}

// assigning to new variable names
{p: foo, q: bar = 2} = { p: 1 };
foo // 1
bar // 2

// destructuring objects in method params
test = ({ a, ...rest } = {}) => rest
test({a:1, b:2}) // {b:2}

// computed property names
key = 'z';
({[key]: foo} = {z: 'bar'});
foo // bar

// destructuring of invalid property names
({ 'fizz-buzz': fizzBuzz } = { 'fizz-buzz': true });
fizzBuzz // true

// iteration
var people = [
  {
    name: 'Mike Smith',
    family: {
      mother: 'Jane Smith',
      father: 'Harry Smith',
      sister: 'Samantha Smith'
    },
    age: 35
  },
  {
    name: 'Tom Jones',
    family: {
      mother: 'Norah Jones',
      father: 'Richard Jones',
      brother: 'Howard Jones'
    },
    age: 25
  }
];

for (var {name: n, family: {father: f}} of people) {
  console.log(`Name: ${n}, Father: ${f}`);
}

// "Name: Mike Smith, Father: Harry Smith"
// "Name: Tom Jones, Father: Richard Jones"

// destructuring with iterables/generators
function* fibs() {
  var a = 0;
  var b = 1;
  while (true) {
    yield a;
    [a, b] = [b, a + b];
  }
}

var [a, b, c, x, y, z] = fibs();