A description
Symbols JavaScript is a basic data type in the new version introduced es6, wherein each Symbol () returned from Symbol values are unique.
Second, the basic usage
- Object is added to the user a unique key
const id = Symbol('id')
let user = {
value: '999',
id: '001',
[id]: 1001
}
console.log(user) // {value: "999", id: 1, Symbol(id): 1001}
console.log(user[id]) // 1001
Value of symbol can not be repeated, but may be modified
// 接上之前的代码
user[id] = 2002
console.log(user[id]) // 2002
Three, Symbol Registry
- The Symbol () returns at each use unique symbol values are
- symbol Symbol.for () method created a global symbol will be placed in the registry
- Symbol.keyFor () needs to pass a Symbol object, the object's return to the global register value of Symbol
Symbol.for("bar") === Symbol.for("bar"); // true
Symbol("bar") === Symbol("bar"); // false
const sym = Symbol.for("mario")
Symbol.keyFor(sym) // mario
const id = Symbol('id')
Symbol.keyFor(id) // undefined
END
