let a, b, rest;
[a, b] = [10, 20];

console.log(a);
// Expected output: 10

console.log(b);
// Expected output: 20

[a, b, ...rest] = [10, 20, 30, 40, 50];

console.log(rest);
// Expected output: Array [30, 40, 50]

let a, b, rest;
[a, b] = [10, 20];
console.log(a); // 10
console.log(b); // 20

[a, b, ...rest] = [10, 20, 30, 40, 50];
console.log(a); // 10
console.log(b); // 20
console.log(rest); // [30, 40, 50]

({ a, b } = { a: 10, b: 20 });
console.log(a); // 10
console.log(b); // 20

// Stage 4(finished) proposal
({ a, b, ...rest } = { a: 10, b: 20, c: 30, d: 40 });
console.log(a); // 10
console.log(b); // 20
console.log(rest); // {c: 30, d: 40}

const x = [1, 2, 3, 4, 5];

const x = [1, 2, 3, 4, 5];
const [y, z] = x;
console.log(y); // 1
console.log(z); // 2

const foo = ["one", "two", "three"];

const [red, yellow, green] = foo;
console.log(red); // "one"
console.log(yellow); // "two"
console.log(green); // "three"

let a, b;

[a, b] = [1, 2];
console.log(a); // 1
console.log(b); // 2

let a, b;

[a = 5, b = 7] = [1];
console.log(a); // 1
console.log(b); // 7

let a = 1;
let b = 3;

[a, b] = [b, a];
console.log(a); // 3
console.log(b); // 1

const arr = [1, 2, 3];
[arr[2], arr[1]] = [arr[1], arr[2]];
console.log(arr); // [1,3,2]

function f() {
  return [1, 2];
}

let a, b;
[a, b] = f();
console.log(a); // 1
console.log(b); // 2

function f() {
  return [1, 2, 3];
}

const [a, , b] = f();
console.log(a); // 1
console.log(b); // 3

[, ,] = f();

const [a, ...b] = [1, 2, 3];
console.log(a); // 1
console.log(b); // [2, 3]

const [a, ...b,] = [1, 2, 3];

// SyntaxError : 
// 

function parseProtocol(url) {
  const parsedURL = /^(\w+)\:\/\/([^\/]+)\/(.*)$/.exec(url);
  if (!parsedURL) {
    return false;
  }
  console.log(parsedURL); // ["https://developer.mozilla.org/en-US/Web/JavaScript", "https", "developer.mozilla.org", "en-US/Web/JavaScript"]

  const [, protocol, fullhost, fullpath] = parsedURL;
  return protocol;
}

console.log(
  parseProtocol("https://developer.mozilla.org/en-US/Web/JavaScript"),
); // "https"

const o = { p: 42, q: true };
const { p, q } = o;

console.log(p); // 42
console.log(q); // true

let a, b;

({ a, b } = { a: 1, b: 2 });

const o = { p: 42, q: true };
const { p: foo, q: bar } = o;

console.log(foo); // 42
console.log(bar); // true

const { a = 10, b = 5 } = { a: 3 };

console.log(a); // 3
console.log(b); // 5

const { a: aa = 10, b: bb = 5 } = { a: 3 };

console.log(aa); // 3
console.log(bb); // 5

const user = {
  id: 42,
  displayName: "jdoe",
  fullName: {
    firstName: "John",
    lastName: "Doe",
  },
};

function userId({ id }) {
  return id;
}

function whois({ displayName, fullName: { firstName: name } }) {
  return `${displayName} is ${name}`;
}

console.log(userId(user)); // 42
console.log(whois(user)); // "jdoe is John"

function drawChart({
  size = "big",
  coords = { x: 0, y: 0 },
  radius = 25,
} = {}) {
  console.log(size, coords, radius);
  // do some chart drawing
}

drawChart({
  coords: { x: 18, y: 30 },
  radius: 30,
});

const metadata = {
  title: "Scratchpad",
  translations: [
    {
      locale: "de",
      localization_tags: [],
      last_edit: "2014-04-14T08:43:37",
      url: "/de/docs/Tools/Scratchpad",
      title: "JavaScript-Umgebung",
    },
  ],
  url: "/zh-TW/docs/Tools/Scratchpad",
};

let {
  title: englishTitle, // rename
  translations: [
    {
      title: localeTitle, // rename
    },
  ],
} = metadata;

console.log(englishTitle); // "Scratchpad"
console.log(localeTitle); // "JavaScript-Umgebung"

const 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 (const {
  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"

let key = "z";
let { [key]: foo } = { z: "bar" };

console.log(foo); // "bar"

let { a, b, ...rest } = { a: 10, b: 20, c: 30, d: 40 };
a; // 10
b; // 20
rest; // { c: 30, d: 40 }

const foo = { "fizz-buzz": true };
const { "fizz-buzz": fizzBuzz } = foo;

console.log(fizzBuzz); // "true"

const props = [
  { id: 1, name: "Fizz" },
  { id: 2, name: "Buzz" },
  { id: 3, name: "FizzBuzz" },
];

const [, , { name }] = props;

console.log(name); // "FizzBuzz"