ES6初步了解原始数据类型Symbol的用法

    let sy = Symbol()

    let sy = Symbol.for()

    let sy = Symbol("name")
    let sy1 = Symbol("name")
    console.log(sy === sy1) //false

    let sy = Symbol.for("name")
    let sy1 = Symbol.for("name")
    console.log(sy === sy1) // true

    let sy = Symbol()
    console.log(sy + 1) //报错
    console.log(sy > 1) //报错
    console.log(sy + "1") //报错

    let sy = Symbol("sy1")
    const obj = {}
    obj[sy] = "私有的"
    console.log(obj)

    let sy = Symbol("sy1")
    const obj = {
        [sy] : "私有的"
    } 
    console.log(obj)

    const obj = {
        sy : Symbol("私有的")
    } 
    console.log(obj)

    let sy = Symbol.for("hello")
    console.log(Symbol.keyFor(sy))//hello

//获取成功
console.log(obj[sy]) //私有的

console.log(obj.sy) //undefined

    let sy = Symbol("hello")
    const obj = {
        name:"张三",
        age:18,
        
    }
    obj[sy] = "私有的"
    for(let k in obj) {
        console.log(obj) //{name: '张三', age: 18, Symbol(hello): '私有的'}
        console.log(k) //name age
        console.log(obj[k]) //张三 18
    }

    let sy = Symbol("hello")
    const obj = {
        name:"张三",
        age:18    
    }
    obj[sy] = "私有的"
    let a = Object.getOwnPropertySymbols(obj)
    console.log(a)