[Javascript] 객체에 특정 key가 있는지 확인 / Object.keys(obj).includes(key), key in obj

Object.keys(obj).includes(key) 

var obj = {'a': 1, 'b': 2, 'c': 3};

console.log(Object.keys(obj).includes('a')); // true

console.log(Object.keys(obj).includes('abc')); // false

key in obj

var obj = {'a': 1, 'b': 2, 'c': 3};

console.log('a' in obj); // true

console.log('abc' in obj); // false