关于javascript:ES6对象扩展

明天小编和大家一块聊聊ES6中对对象的扩大语法，还有一些罕用的语法，置信在不久的未来，必定会在Vue中看到对象的影子。大家还能够关注我的微信公众号，蜗牛全栈。
一、属性的简洁表示法：次要针对值用变量示意，并且键和值的变量统一
1、一般对象申明

let obj = {    name:"lilei",    age:34}console.log(obj)

2、简洁表示法

let name = "lilei"let age = 34let obj = {    name,    age}

3、属性名表达式：次要针对键为变量的状况，须要将变量加上方括号即可

let s = "school"let obj = {    name:"lilei",    age:34,    s:"school"}console.log(obj) // {name:"lilei",age:34,s:"school"}let s = "school"let obj = {    name:"lilei",    age:34,    [s]:"school"}console.log(obj) // {name:"lilei",age:34,school:"school"}

4、对象内的函数

let s = "school"let obj = {    name:"lilei",    age:34,    [s]:"school",    study:function(){        console.log(this.name+"正在学习")    }}obj.study() // lilei正在学习let s = "school"let obj = {    name:"lilei",    age:34,    [s]:"school",    study:() => {        console.log(this.name+"正在学习")    }}obj.study() // 报错：can't read property 'name' of undefind(起因就是箭头函数的this指向问题，参见小编的箭头函数文章)let s = "school"let obj = {    name:"lilei",    age:34,    [s]:"school",    study(){        console.log(this.name+"正在学习")    }}obj.study() // lilei正在学习

二、Object.is()：相当于严格判断的三个等号

console.log(Object.is(2,'2')) // falseconsole.log(Object.is(NaN,NaN)) // trueconsole.log(Object.is(+0,-0)) // falselet obj1 = {    name:"lilei",    age:34}let obj2 = {    name:"lilei",    age:34}console.log(obj1 == obj2) // false console.log(Object.is(obj1,obj2)) // false 援用类型的堆内存地址不统一let obj1 = {    name:"lilei",    age:34}let obj2 = obj1console.log(Object.is(obj1,obj2)) // true 援用类型的堆内存地址统一

三、扩大运算符与Object.assign()

let x = {    a:3,    b:4}let y = {...x}console.log(y) // {a:3,b:4}let x = {    a:3,    b:4}let y = {}Object.assign(y,x)console.log(y) // {a:3,b:4}let x = {    a:3,    b:4}let y = {    c:5,    a:6}Object.assign(y,x)console.log(y) // {a:6,b:4,c:5}

四、in：判断数组指定下标是否存在值；判断对象是否存在指定键

let x = {    a:3,    b:4}console.log("a" in x) // truelet arr = [1,2,3]console.log(3 in arr) // false 判断下表为3的地位是否有值，而不是值3

五、对象的遍历
办法1

let obj = {    name:"lilei",    age:34,    school:"School"}for(let key in obj){    console.log(key,obj[key])}

办法2

let obj = {    name:"lilei",    age:34,    school:"School"}Object.keys(obj).forEach(key => {    console.log(key,obj[key])})

办法3

let obj = {    name:"lilei",    age:34,}Object.getOwnPropertyNames(obj).forEach(key => {    console.log(key,obj[key])})

办法4

let obj = {    name:"lilei",    age:34,    school:"School"}Reflect.ownKeys(obj).forEach(key => {    console.log(key,obj[key])})