What is the difference between Reflect.ownKeys(obj) and Object.keys(obj)?

Question

Testing them out in a real simple case yields the same output:

const obj = {a: 5, b: 5};
console.log(Reflect.ownKeys(obj));
console.log(Object.keys(obj));

// Re         


        

Answer 1

Object.keys() returns an array of strings, which are the object's own enumerable properties.

Reflect.ownKeys(obj) returns the equivalent of:

Object.getOwnPropertyNames(target).
                   concat(Object.getOwnPropertySymbols(target))

The Object.getOwnPropertyNames() method returns an array of all properties (enumerable or not) found directly upon a given object.

The Object.getOwnPropertySymbols() method returns an array of all symbol properties found directly upon a given object.

var testObject = {};
Object.defineProperty(testObject, 'myMethod', {
    value: function () {
        alert("Non enumerable property");
    },
    enumerable: false
});

//does not print myMethod since it is defined to be non-enumerable
console.log(Object.keys(testObject));

//prints myMethod irrespective of it being enumerable or not.
console.log(Reflect.ownKeys(testObject));