In what order does Object.keys list these properties?

const obj = {
  b: 1,
  2: 1,
  a: 1,
  1: 1,
  "-1": 1,
  "01": 1,
};
obj.c = 1;
obj[0] = 1;
 
console.log(Object.keys(obj));
console.log(JSON.stringify({ z: 1, 10: 1, y: 1, 9: 1 }));