Check if an Object has a Property

let users = {
  Alan: {
    age: 27,
    online: true
  },
  Jeff: {
    age: 32,
    online: true
  },
  Sarah: {
    age: 48,
    online: true
  },
  Ryan: {
    age: 19,
    online: true
  }
};

function isEveryoneHere(obj) {
  if (
    obj.hasOwnProperty("Alan") &&
    obj.hasOwnProperty("Jeff") &&
    obj.hasOwnProperty("Sarah") &&
    obj.hasOwnProperty("Ryan")
  ) {
    return true;
  }
  return false;
}