keys, getOwnPropertyNames, for...in

const obj = {
    name: 'jaewoo',
    number: '010-000-0000'
}

// set prototype object
Object.setPrototypeOf(obj, {protoProp: 'parent'});

// set non enumerable property
Object.defineProperty(obj, 'gender', {enumerable: false})

obj 객체를 base로 Object.keys, for...in, getOwnPropertyNames를 비교한다.

 

Object.keys

// returns enumerable properties
Object.keys(obj)
// ['name', 'number']

Object.getOwnPropertyNames

// returns enumerable & non-enumerable properties
Object.getOwnPropertyNames(obj)
// ['name', 'number', 'gender']

for...in

// returns enumerable properties (but, only string keys)
// including inherited enumerable properties
for(let key in obj){
  console.log(key)
};
// name
// number
// protoProp

Summary

	Object.keys	Object.getOwnPeropertyNames	for...in
enumerable	O	O	O
non-enumerable	X	O	X
inherited	X	X	O