ES6函数与对象的语法糖

1.函数默认参数

• 与 Python 的区别 http://effbot.org/zone/default-values.htm

2.剩余参数(3种写法)

function sum(message){
//     let args = Array.prototype.slice.call(arguments) // ES5 将伪数组变为真数组
//     let args = Array.from(arguments)                 // ES6 将伪数组变为真数组
    let args = [...arguments]                        // ES6 将伪数组变为真数组
    
    let numbers = args.slice(1)
    result =  numbers.reduce((p,v)=>p+v,0)
    return message + result

}

sum('结果是',1,2,3,4,5,6,7,8,9,10)

function sum(message,...numbers){
    
    result =  numbers.reduce((p,v)=>p+v,0)
    return message + result

}

sum('结果是',1,2,3,4,5,6,7,8,9,10)

3.展开操作

let array1 = [1,2,3,4,5,6]
let [a,b,c,...array2] = array1
console.log(array2)

打印出的结果为[4,5,6]

var array1 = [1,2,3,4,5,6]
var [,,,...array2] = array1
console.log(array2)

打印出的结果还是为[4,5,6]

var array1 = [1,2,3,4,5,6]
var [...array2] = array1
console.log(array2)

打印出的结果为[1,2,3,4,5,6]

var array1 = [1,2,3,4,5,6]
var array2 = [0,...array1,7]
console.log(array2) 

打印出的结果为[0,1,2,3,4,5,6,7]

4.解构赋值

var a = 1
var b = 2;  //分号在文件里不可以省略，在控制台里面可以省略

[a,b] = [b,a]
console.log(a)
console.log(b)

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

let {name, age} = frank

解构赋值 解构赋值 解构赋值 解构赋值 解构赋值 解构赋值 解构赋值，把name重命名为xinming,如果没取到xinming,那默认值为Tom 浅拷贝 浅拷贝 对象合并 对象合并

5.对象属性加强

对象属性加强

var x = 1
var y = 2
var obj1 = {name:1,age:2}

var obj2 = {
    z:1,
    x,
    y,
    ...obj1,
    sayHi(){},
    sayBye(){},
    sayByeBye:function(){

    }
}

console.log(obj2)

属性增强 image.png