es6基础入门变量的解构赋值

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

 let [foo, [[bar], baz]] = [1, [[2], 3]];
 foo //
 bar //
 baz //

 let [ , , third] = ["foo", "bar", "baz"];
 third // "baz"

 let [x, , y] = [1, 2, 3];
 x //
 y //

 let [head, ...tail] = [1, 2, 3, 4];
 head //
 tail // [2, 3, 4]

 let [x, y, ...z] = ['a'];
 x // "a"
 y // undefined
 z // []

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

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

 let [foo = true] = [];
 foo // true

 let [x, y = 'b'] = ['a']; // x='a', y='b'
 let [x, y = 'b'] = ['a', undefined]; // x='a', y='b'

 let [x = 1] = [undefined];
 x //

 let [x = 1] = [null];
 x // null

 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

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

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

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

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

 let obj = { first: 'hello', last: 'world' };
 let { first: f, last: l } = obj;
 f // 'hello'
 l // 'world'

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