text: 
  const o = {
      a: 1,
      b: 2,
      c: 3
  };
  
  console.log(Object.keys(o));
  
  console.log(JSON.stringify(o));
  
  o.a = 42;
  console.log(JSON.stringify(o));
  
  const p = {};
  
  Object.defineProperty(p, 'a', {
      value: 42,
      writable: false
  });
  
  
  console.log(Object.keys(p));
  
  console.log(JSON.stringify(p));
  