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Challenge 109: What's My Age Again?

curriculum/challenges/english/blocks/daily-coding-challenges-javascript/68ffb91507a5b645769328cc.md

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--description--

Given the date of someone's birthday in the format YYYY-MM-DD, return the person's age as of November 27th, 2025.

  • Assume all birthdays are valid dates before November 27th, 2025.
  • Return the age as an integer.
  • Be sure to account for whether the person has already had their birthday in 2025.

--hints--

calculateAge("2000-11-20") should return 25.

js
assert.equal(calculateAge("2000-11-20"), 25);

calculateAge("2000-12-01") should return 24.

js
assert.equal(calculateAge("2000-12-01"), 24);

calculateAge("2014-10-25") should return 11.

js
assert.equal(calculateAge("2014-10-25"), 11);

calculateAge("1994-01-06") should return 31.

js
assert.equal(calculateAge("1994-01-06"), 31);

calculateAge("1994-12-14") should return 30.

js
assert.equal(calculateAge("1994-12-14"), 30);

--seed--

--seed-contents--

js
function calculateAge(birthday) {

  return birthday;
}

--solutions--

js
function calculateAge(birthday) {
  const today = new Date("2025-11-27");
  const [year, month, day] = birthday.split("-").map(Number);
  const birthDate = new Date(year, month - 1, day);

  let age = today.getFullYear() - birthDate.getFullYear();

  if (
    today.getMonth() < birthDate.getMonth() ||
    (today.getMonth() === birthDate.getMonth() && today.getDate() < birthDate.getDate())
  ) {
    age--;
  }

  return age;
}