text: let ages = new Map();
  
  let fun = (n) => n * n
  
  ages.set('Julia', 62);
  ages.set('Liang', 22);
  ages.set('Boris', 43);
  ages.set('Square', fun);
  
  console.log(ages.get('Julia'));
  console.log(ages.get('Liang'));
  console.log(ages.has('toString'));
  console.log(ages.get('Square')(6));