Symbol 如何与字符串操作
- const s = Symbol('s')
- // 强制类型转换会抛类型错误
- console.log(s + '/s'); // TypeError: Cannot convert a Symbol value to a string
- console.log(`${s}/s`) // TypeError: Cannot convert a Symbol value to a string
- // 只能先进行强制转换
- console.log(String(s) + '/s');
- console.log(s.toString() + '/s');
哪些与属性键相关的方法可以识别 Symbol
下列方法会把 Symbol 识别为属性 key
- - Reflect.ownKeys()
- - Object.getOwnPropertySymbols()
- [] 访问符
- const name = Symbol('name')
- const o = {
- [name]: 'kobe',
- a: 1,
- b: 2
- }
- const copy = Object.assign(Object.create(null), o)
- console.log(Reflect.ownKeys(o)); // [ 'a', 'b', Symbol(name) ]
- console.log(Object.getOwnPropertySymbols(o)); // [ Symbol(name) ]
- console.log(o[name]); // kobe
- console.log(Reflect.ownKeys(copy)); // [ 'a', 'b', Symbol(name) ]
下列方法不会识别 Symbol 作为属性 key
- - Object.keys()
- - Object.getOwnPropertyNames()
- - for-in loop
- const name = Symbol('name')
- const o = {
- [name]: 'kobe',
- a: 1,
- b: 2
- }
- for (let key in o) {
- console.log(key); // a b
- }
- console.log(Object.keys(o)); // [ 'a', 'b' ]
- console.log(Object.getOwnPropertyNames(o)); // [ 'a', 'b' ]
来源: https://juejin.im/post/5c8085d5e51d4542176d1322