// es6
let arr = [1, 2, 3];
let [a, b, c] = arr;// es5
var arr = [1, 2, 3];
var a = arr[0];
var b = arr[1];
var c = arr[2];

function sum(x,y){x=x||10;y=y||20;return x+y;}

ES6的默认值写法：

function sum(x = 10, y = 20) {return x + y;
}console.log(add());

注意：1、箭头函数是匿名函数，不能作为构造函数，不能使用new

let FunConstructor = () => {console.log('lll');
}let fc = new FunConstructor();

function A(a){console.log(arguments);
}
A(1,2,3,4,5,8);  //  [1, 2, 3, 4, 5, 8, callee: ƒ, Symbol(Symbol.iterator): ƒ]
let B = (b)=>{console.log(arguments);
}
B(2,92,32,32);   // Uncaught ReferenceError: arguments is not defined
let C = (...c) => {console.log(c);
}
C(3,82,32,11323);  // [3, 82, 32, 11323]

const map1 = new Map()
const objkey = {p1: 'v1'}map1.set(objkey, 'hello')
console.log(map1.get(objkey))

结果：

hello

const map2 = new Map([['name', 'Aissen'],['age', 12]
])
console.log(map2.get('name'))
console.log(map2.get('age'))

Aissen
12

// 没有参数的情况
var s1 = Symbol();
var s2 = Symbol();s1 === s2 // false// 有参数的情况
var s1 = Symbol("foo");
var s2 = Symbol("foo");s1 === s2 // false

class Animal {constructor(){this.type = 'animal'}says(say){console.log(this.type + ' says ' + say)}
}let animal = new Animal()
animal.says('hello') //animal says helloclass Cat extends Animal {constructor(){super()this.type = 'cat'}
}let cat = new Cat()
cat.says('hello') //cat says hello

$("#result").append("There are <b>" + basket.count + "</b> " +"items in your basket, " +"<em>" + basket.onSale +"</em> are on sale!"
);

$("#result").append(`There are <b>${basket.count}</b> itemsin your basket, <em>${basket.onSale}</em>are on sale!
`);

let m = new Map([[1, 2], [2, 4], [4, 8]]);
Array.from(m);
// [[1, 2], [2, 4], [4, 8]]

function f() {return Array.from(arguments);
}
f(1, 2, 3);
// [1, 2, 3]

Array.from([1, 2, 3], x => x + x);
// [2, 4, 6]// Generate a sequence of numbers
// Since the array is initialized with `undefined` on each position,
// the value of `v` below will be `undefined`
Array.from({length: 5}, (v, i) => i);
// [0, 1, 2, 3, 4]

//数组去重合并function combine(){ let arr = [].concat.apply([], arguments);  //concat() 方法用于连接两个或多个数组。该方法不会改变现有的数组，仅仅返回被连接数组的一个副本。

return Array.from(new Set(arr));

} var m = [1, 2, 2], n = [2,3,3];
console.log(combine(m,n));                     // [1, 2, 3]

Array.of(7);       // [7]
Array.of(1, 2, 3); // [1, 2, 3]

Array(7);          // [ , , , , , , ]
Array(1, 2, 3);    // [1, 2, 3]

if (!Array.of) {Array.of = function() {return Array.prototype.slice.call(arguments);};
}

const a = {a: 1, b: 2} const b = {b: 3, c: 4} console.log({...a, ...b, c: 5}) // {a: 1, b: 3, c: 5} // 相当于 Object.assign(a, b, {c: 5})

//content.js
define('content.js', function(){return 'A cat';
})

//index.js
require(['./content.js'], function(animal){console.log(animal);   //A cat
})

//index.js
var animal = require('./content.js')//content.js
module.exports = 'A cat'

//index.js
import animal from './content'//content.js
export default 'A cat'

//content.jsexport default 'A cat'
export function say(){return 'Hello!'
}
export const type = 'dog' 

//index.jsimport { say, type } from './content'
let says = say()
console.log(`The ${type} says ${says}`)  //The dog says Hello

//index.jsimport animal, { say, type } from './content'
let says = say()
console.log(`The ${type} says ${says} to ${animal}`)
//The dog says Hello to A cat

//index.jsimport animal, { say, type as animalType } from './content'
let says = say()
console.log(`The ${animalType} says ${says} to ${animal}`)
//The dog says Hello to A cat

//index.jsimport animal, * as content from './content'
let says = content.say()
console.log(`The ${content.type} says ${says} to ${animal}`)
//The dog says Hello to A cat