var [a, b, c] = [1, 2, 3];

let [foo, [[bar], baz]] = [1, [[2], 3]];
foo // 1
bar // 2
baz // 3
let [ , , third] = ["foo", "bar", "baz"];
third // "baz"
let [x, , y] = [1, 2, 3];
x // 1
y // 3
let [head, ...tail] = [1, 2, 3, 4];
head // 1
tail // [2, 3, 4]
let [x, y, ...z] = ['a'];
x // "a"
y // undefined
z // []

var [foo] = [];
var [bar, foo] = [1];

let [x, y] = [1, 2, 3];
x // 1
y // 2
let [a, [b], d] = [1, [2, 3], 4];
a // 1
b // 2
d // 4

// 报错let [foo] = 1;
let [foo] = false;
let [foo] = NaN;
let [foo] = undefined;
let [foo] = null;
let [foo] = {};

var [v1, v2, ..., vN ] = array;
let [v1, v2, ..., vN ] = array;
const [v1, v2, ..., vN ] = array;

let [x, y, z] = new Set(["a", "b", "c"]);
x // "a"

function* fibs() {
  var a = 0;
  var b = 1;
  while (true) {
  yield a;
   [a, b] = [b, a + b];
  }
}
var [first, second, third, fourth, fifth, sixth] = fibs();
sixth // 5

var [foo = true] = [];
foo // true
[x, y = 'b'] = ['a']; // x='a', y='b'
[x, y = 'b'] = ['a', undefined]; // x='a', y='b'

var [x = 1] = [undefined];
x // 1
var [x = 1] = [null];
x // null

function f() {
console.log('aaa');
}
let [x = f()] = [1];
//等价于
let x;
if ([1][0] === undefined) {
  x = f();
} else {
  x = [1][0];
}

let [x = 1, y = x] = []; // x=1; y=1
let [x = 1, y = x] = [2]; // x=2; y=2
let [x = 1, y = x] = [1, 2]; // x=1; y=2
let [x = y, y = 1] = []; // ReferenceError

var { foo, bar } = { foo: "aaa", bar: "bbb" };
foo // "aaa"
bar // "bbb"

var { bar, foo } = { foo: "aaa", bar: "bbb" };
foo // "aaa"
bar // "bbb"
var { baz } = { foo: "aaa", bar: "bbb" };
baz // undefined

var { foo: foo, bar: bar } = { foo: "aaa", bar: "bbb" };

var { foo: baz } = { foo: "aaa", bar: "bbb" };
baz // "aaa"
foo // error: foo is not defined

let foo;
let {foo} = {foo: 1}; 
// SyntaxError: Duplicate declaration "foo"
let baz;
let {bar: baz} = {bar: 1}; 
// SyntaxError: Duplicate declaration "baz"

let foo;
({foo} = {foo: 1}); // 成功
let baz;
({bar: baz} = {bar: 1}); // 成功

var obj = {
  p: [
   "Hello",
   { y: "World" }
  ]
};
var { p: [x, { y }] } = obj;
x // "Hello"
y // "World"

var node = {
  loc: {
   start: {
     line: 1,
     column: 5
   }
  }
};
var { loc: { start: { line }} } = node;
line // 1
loc // error: loc is undefined
start // error: start is undefined

let obj = {};
let arr = [];
({ foo: obj.prop, bar: arr[0] } = { foo: 123, bar: true });
obj // {prop:123}
arr // [true]

var {x = 3} = {};
x // 3
var {x, y = 5} = {x: 1};
x // 1
y // 5
var { message: msg = "Something went wrong" } = {};
msg // "Something went wrong"

var {x = 3} = {x: undefined};
x // 3
var {x = 3} = {x: null};
x // null

var {foo} = {bar: 'baz'};
foo // undefined

// 报错
var {foo: {bar}} = {baz: 'baz'};

// 错误的写法
var x;
{x} = {x: 1};
// SyntaxError: syntax error
// 正确的写法
({x} = {x: 1});

let { log, sin, cos } = Math;

const [a, b, c, d, e] = 'hello';
a // "h"
b // "e"
c // "l"
d // "l"
e // "o"

let {length : len} = 'hello';
len // 5

let {toString: s} = 123;
s === Number.prototype.toString // true
let {toString: s} = true;
s === Boolean.prototype.toString // true

let { prop: x } = undefined; // TypeError
let { prop: y } = null; // TypeError

function add([x, y]){
  return x + y;
}
add([1, 2]); // 3

function move({x = 0, y = 0} = {}) {
  return [x, y];
}
move({x: 3, y: 8}); // [3, 8]
move({x: 3}); // [3, 0]
move({}); // [0, 0]
move(); // [0, 0]

function move({x, y} = { x: 0, y: 0 }) {
return [x, y];
}
move({x: 3, y: 8}); // [3, 8]
move({x: 3}); // [3, undefined]
move({}); // [undefined, undefined]
move(); // [0, 0]

// 全部报错
var [(a)] = [1];
var {x: (c)} = {};
var ({x: c}) = {};
var {(x: c)} = {};
var {(x): c} = {};}
var { o: ({ p: p }) } = { o: { p: 2 } };

// 报错
function f([(z)]) { return z; }

// 全部报错
({ p: a }) = { p: 42 };
([a]) = [5];

[({ p: a }), { x: c }] = [{}, {}];

[(b)] = [3]; // 正确
({ p: (d) } = {}); // 正确
[(parseInt.prop)] = [3]; // 正确

[x, y] = [y, x];

// 返回一个数组
function example() {
  return [1, 2, 3];
}
var [a, b, c] = example();
// 返回一个对象
function example() {
  return {
   foo: 1,
   bar: 2
  };
}
var { foo, bar } = example();

function f([x, y, z]) { ... }
f([1, 2, 3]);
// 参数是一组无次序的值
function f({x, y, z}) { ... }
f({z: 3, y: 2, x: 1});

var jsonData = {
  id: 42,
  status: "OK",
  data: [867, 5309]
};
let { id, status, data: number } = jsonData;
console.log(id, status, number);
// 42, "OK", [867, 5309]

jQuery.ajax = function (url, {
  async = true,
  beforeSend = function () {},
  cache = true,
  complete = function () {},
  crossDomain = false,
  global = true,
  // ... more config
}) {
  // ... do stuff
};

var map = new Map();
map.set('first', 'hello');
map.set('second', 'world');
for (let [key, value] of map) {
  console.log(key + " is " + value);
}
// first is hello
// second is world
// 获取键名
for (let [key] of map) {
// ...
}
// 获取键值
for (let [,value] of map) {
// ...
}

const { SourceMapConsumer, SourceNode } = require("source-map")