【JS ES6】了解Symbol类型

let hd = Symbol();
let edu = Symbol();
console.log(hd == edu);//false

hd.name = 'xiaoxie'
console.log(hd.name);//undefined

//添加描述
let hd = Symbol("坚毅的小解同志");
let edu = Symbol("csdn");
//获取描述
console.log(edu.description);//csdn

//添加描述第二种方法
//重复定义相同内容，指向的是同一个地址，不会产生新的占用  引用地址
let hd = Symbol.for("xiaoxie");
let edu = Symbol.for("xiaoxie");
console.log(hd == edu);//true
//获取描述
console.log(Symbol.keyFor(hd));//xiaoxie

let grade = {
    李四: { js: 100, css: 89 },
    李四: { js: 20, css: 50 },
}
console.log(grade);//{ '李四': { js: 20, css: 50 } }

//对象使用变量需要加上【】
let user1 = '李四';
let user2 = '李四';
let grade = {
    [user1]: { js: 100, css: 89 },
    user2: { js: 20, css: 50 },
}
console.log(grade);//{ '李四': { js: 100, css: 89 }, user2: { js: 20, css: 50 } }

let user1 = {
    name: "李四",
    key: Symbol('李四')
};
let user2 = {
    name: "李四",
    key: Symbol()
};
let grade = {
    [user1.key]: { js: 100, css: 89 },
    [user2.key]: { js: 20, css: 50 },
}
console.log(grade[user1.key]);//{ js: 100, css: 89 }
console.log(grade);//{ [Symbol(李四)]: { js: 100, css: 89 }, [Symbol()]: { js: 20, css: 50 } }

//forin for of 遍历不到Symbol
for (const key in hd) {
    console.log(key);//name
}
for (const iterator of Object.keys(hd)) {
    console.log(iterator);//name
}

//便利Symbol类型
for (const iterator of Object.getOwnPropertySymbols(hd)) {
    console.log(iterator);//Symbol(这是一个Symbol类型)
}
//遍历对象中的所有属性
for (const iterator of Reflect.ownKeys(hd)) {
    console.log(iterator);//name
    //Symbol(这是一个Symbol类型)
}