let sym = Symbol();
// 因?yàn)榉?hào)本身是原始類(lèi)型，所以typeof操作符對(duì)符號(hào)返回symbol
console.log(typeof sym); // symbol

// Symbol的值是唯一的，不會(huì)出現(xiàn)相同值的常量
let genericSymbol = Symbol();
let otherGenericSymbol = Symbol();
console.log(genericSymbol == otherGenericSymbol); // false

// 可以傳入一個(gè)字符串參數(shù)作為對(duì)符號(hào)的描述
let fooSymbol = Symbol('foo');
let otherFooSymbol = Symbol('foo');
console.log(fooSymbol == otherFooSymbol); // false

let genericSymbol = Symbol();
console.log(genericSymbol); // Symbol()

let fooSymbol = Symbol('foo');
console.log(fooSymbol); // Symbol(foo)

let myBoolean = new Boolean();
console.log(typeof myBoolean); // "object"

let myString = new String();
console.log(typeof myString); // "object"

let myNumber = new Number();
console.log(typeof myNumber); // "object"

let mySymbol = new Symbol(); // 報(bào)錯(cuò)，TypeError
console.log(mySymbol);

let mySymbol = Symbol();
let myWarppedSymbol = Object(mySymbol);
console.log(typeof myWarppedSymbol); // "object"

let fooGlobalSymbol = Symbol.for('foo');
console.log(typeof fooGlobalSymbol); // symbol

// 創(chuàng)建新符號(hào)
let fooGlobalSymbol = Symbol.for('foo');
// 重用已有符號(hào)
let otherFooGlobalSymbol = Symbol.for('foo');

console.log(fooGlobalSymbol === otherFooGlobalSymbol); // true

// 使用Symbol()定義
let localSymbol = Symbol('foo');
// 使用全局注冊(cè)表定義
let globalSymbol = Symbol.for('foo');

console.log(localSymbol === globalSymbol); // false

let emptyGlobalSymbol = Symbol.for();
console.log(emptyGlobalSymbol); // Symbol(undefined)

// 創(chuàng)建全局符號(hào)
let s = Symbol.for('foo');
console.log(Symbol.keyFor(s)); // foo

// 創(chuàng)建普通符號(hào)
let s2 = Symbol('bar');
console.log(Symbol.keyFor(s2)); // undefined

Symbol.keyFor(123); // TypeError: 123 is not a symbol

let s1 = Symbol('foo'),
    s2 = Symbol('bar'),
    s3 = Symbol('baz'),
    s4 = Symbol('qux');

let o = {
    // [屬性]，會(huì)對(duì)屬性進(jìn)行讀取，并且轉(zhuǎn)換成字符串。[s1]是讀取了Symbol的字符串鍵'foo'
    [s1]: 'foo val'
};
// 或 o[s1] = 'foo val';
console.log(o); // { [Symbol(foo)]: 'foo val' }

Object.defineProperty(o, s2, { value: 'bar val' });
console.log(o); // {Symbol(foo): foo val, Symbol(bar): bar val}

Object.defineProperties(o, {
    [s3]: { value: 'baz val' },
    [s4]: { value: 'qux val' }
});
console.log(o); // {Symbol(foo): foo val, Symbol(bar): baz val,
                //  Symbol(foo): foo val, Symbol(bar): qux val}

let s1 = Symbol('foo'),
    s2 = Symbol('bar');

let o = {
    [s1]: 'foo val',
    [s2]: 'bar val',
    baz: 'baz val',
    qux: 'qux val'
};

// Object.getOwnPropertySymbols()返回對(duì)象實(shí)例的符號(hào)屬性數(shù)組
console.log(Object.getOwnPropertySymbols(o)); // [ Symbol(foo), Symbol(bar) ]

// Object.getOwnPropertyNames()返回對(duì)象實(shí)例的常規(guī)屬性數(shù)組
console.log(Object.getOwnPropertyNames(o)); // [ 'baz', 'qux' ]

// Object.getOwnPropertyDescriptors()會(huì)返回同時(shí)包含常規(guī)和符號(hào)屬性描述符的對(duì)象
console.log(Object.getOwnPropertyDescriptors(o));
// {
//     baz: {
//       value: 'baz val',
//       writable: true,
//       enumerable: true,
//       configurable: true
//     },
//     qux: {
//       value: 'qux val',
//       writable: true,
//       enumerable: true,
//       configurable: true
//     },
//     [Symbol(foo)]: {
//       value: 'foo val',
//       writable: true,
//       enumerable: true,
//       configurable: true
//     },
//     [Symbol(bar)]: {
//       value: 'bar val',
//       writable: true,
//       enumerable: true,
//       configurable: true
//     }
//   }

// Reflect.ownKeys()會(huì)返回兩種類(lèi)型的鍵
console.log(Reflect.ownKeys(o)); // [ 'baz', 'qux', Symbol(foo), Symbol(bar) ]

let o = {
    [Symbol('foo')]: 'foo val',
    [Symbol('bar')]: 'bar val'
};
console.log(o); // { [Symbol(foo)]: 'foo val', [Symbol(bar)]: 'bar val' }

let barSymbol = Object.getOwnPropertySymbols(o).find((Symbol) => 
				Symbol.toString().match(/bar/));
console.log(barSymbol); // Symbol(bar)

const name = Symbol('name');
const obj = {
    [name]: 'ClickPaas',
}

const speak = Symbol();
class Person {
    [speak]() {
        console.log(123)
    }
}
let person = new Person()
console.log(person[speak]())