JavaScript: Reflect.ownKeys

New in JS2015.

Reflect.ownKeys(obj)

Return a Array of the object's keys. (including Symbol keys and non-enumerable keys.)

const obj = {
 "y": 3,
 [Symbol("x")] : 4,
};

// list all properties of a object
console.log( Reflect.ownKeys(obj) ); // prints [ 'y', Symbol(x) ]