SOURCE

var a = [{c:1}]
var b = a.slice()
a[0].c++
console.log(b);

const stu1 = Symbol('张三')
const stu2 = Symbol('张三')

const grade = {
    [stu1]:{address: 'xxx' , tel: '1111'},
    [stu2]:{address:'aaa',tel:'2222'}
}

console.log(grade[stu1])
console.log(grade[stu2])
console.log(grade)

const sym = Symbol('imooc')

class User {
    constructor(name) {
        this.name = name
    }
    getName(){
        return this.name + this[sym]
    }
}

const user = new User('name')
console.log(user.name)
//for in 只能去到不是symbol 属性
for(let key in user){
    console.log(key)
}