Object properties

properties.js

const obj = {
  [Symbol('my_key')]  : 1, 
   enum               : 2, 
   nonEnum            : 3
};

Object.defineProperty(obj, 'nonEnum', { enumerable: false }); // Making 'nonEnum' as not enumerable.

// Ignores symbol-valued property keys:
> Object.getOwnPropertyNames(obj)
['enum', 'nonEnum']

// Ignores string-valued property keys:
> Object.getOwnPropertySymbols(obj)
[Symbol(my_key)]

// Considers all kinds of keys:
> Reflect.ownKeys(obj)
[Symbol(my_key),'enum', 'nonEnum']

// Only considers enumerable property keys that are strings:
> Object.keys(obj)
['enum']