how-many-weeks-old-are-you.js

'use strict';

const Readline = require('node:readline');
const RL = Readline.createInterface({
  input: process.stdin,
  output: process.stdout,
});

const main = async function () {
  const year = await runReadline('What year were you born in? ', checkerInt);
  const month = await runReadline('What month were you born on? ', checkerInt);
  const day = await runReadline('What day of the month were you born on? ', checkerInt);
  const offset = await runReadline('What timezone were you born in? Please type in offset. eg. Japan 9, SF -8 ', checkerInt);
  const [sign, zeroPadHours] = destructureOffset(offset);
  const bday = new Date(`${year}-${month}-${day}T12:00:00.000${sign ? '+' : '-'}${zeroPadHours}:00`);
  console.log(`You are ${getWeek(bday)} weeks old`);

  process.exit(0);
};

const getWeek = function (date) {
  return Math.floor( (Date.now() - date.valueOf()) / (60 * 60 * 24 * 7 * 1000))
};

const destructureOffset = function (num) {
  const abs = Math.abs(num);
  const zeroPad = `0${abs}`.slice(-2);
  return num > 0 ? [true, zeroPad] : [false, zeroPad];
};

const checkerInt = function (str) {
  const result = parseInt(str, 10);
  if (isNaN(result)) {
    return null;
  }
  return result;
}

const runReadline = async function (question, checker) {
  let count = 0;
  let result;
  loop:while (true) {
    const answer = checker(await runReadlineImpl(question));
    if (answer !== null) {
      result = answer;
      break loop;
    } else {
      ++count;
      if (count > 5) {
        console.log('Too many invalid inputs. Exiting.');
        process.exit(1);
      }
      console.log('Invalid input. Please try again.');
    }
  }
  return result;
};

const runReadlineImpl = function (question) {
  return new Promise((resolve, reject) => {
    try {
      RL.question(question, (answer) => {
        resolve(answer);
      });
    } catch (err) {
      reject(err);
    }
  });
};

main();