ES6 from getting started to mastering 09: symbol type

explain

ES6 From entry to Mastery Series （ whole 23 speak ） Learning notes .

Symbol type

Raw data type ：Symbol, It represents a unique value .

The greatest use ： Private variables used to define objects .

const kaimo = Symbol("kaimo");
const kaimo2 = Symbol("kaimo");
console.log(kaimo === kaimo2);

If you use Symbol Variables in defined objects , When taking values, you must use [ Variable name ].

let s = Symbol('s');
console.log(s);
let obj = {
    
	[s]: "kaimo"
}
console.log(obj[s]);

Be careful ： use Symbol Variables in defined objects cannot be for in Go through it

let s = Symbol('s');
let obj = {
    
	[s]: "kaimo",
	ss: "kaimo2"
}
for(let key in obj) {
    
	console.log(key)
}

You should use Object.getOwnPropertySymbols perhaps Reflect.ownKeys To deal with .

let s = Symbol('s');
let obj = {
    
	[s]: "kaimo",
	ss: "kaimo2"
}
console.log(Object.keys(obj))
console.log("--------------")
console.log(Object.getOwnPropertySymbols(obj))
console.log("--------------")
console.log(Reflect.ownKeys(obj))