使用引用而不是新对象来保存内存和巨大的GC?

// would this make sense if the # of Persons is so high that
// the probability of all dates being used is close to 100%?
class BirthDate {
  constructor (props) {
    this.day = props.day;
    this.month = props.month;
  }
  // would also be nice to add methods, e.g:
  getAge (currentDateTime) { /* .. */ }
}

let dates = {
  '3.7': new BirthDate({day: 3, month: 7}),
  '4.7': new BirthDate({day: 4, month: 7})
  // etc, 1-30 days for 1-12 months
};

class Person {
  constructor (props) {
    this.id = props.id;
    this.birthDate = props.birthDate;
  }
}

let people = { lookup: {}, array: [] };
for (let i = 0; i < 1000; i++) {
  const person = new Person({
    id: `whatever-${i}`,
    birthDate: {day: 3, month: 7},   // <- new location in memory each time, lots of duplicates
    // birthDate: dates[`${3}.${7}`] // <- should use only reference right?
  });
  people.lookup[person.id] = person;
  people.array.push(person);
}

console.log(people);