main.js

/*
 * Your program must print string with the number of years and months and the total number of days between the dates.
 * Dates are provided in dd.mm.yyyy format.
 * You are not allowed to plug in JS libraries such as moment.js or date-fns directly into the code. All code need to be written in this file.
 *
 * Result must be shown as a string in years, months and total days. If years or months are 0, then it should not be displayed in the output.
 *
 * Example:
 * Input: ['01.01.2000', '01.01.2016']
 * Output:
 * '16 years, total 5844 days'
 *
 * Example 2:
 * Input: ['01.11.2015', '01.02.2017']
 *
 * Output:
 * '1 year, 3 months, total 458 days'
 */
const dates = [
  ["01.01.2000", "01.01.2016"],
  ["01.01.2016", "01.08.2016"],
  ["01.11.2015", "01.02.2017"],
  ["17.12.2016", "16.01.2017"],
  ["01.01.2016", "01.01.2016"],
  ["28.02.2015", "13.04.2018"],
  ["28.01.2015", "28.02.2015"],
  ["17.03.2022", "17.03.2023"],
  ["17.02.2024", "17.02.2025"],
];

// Receive string of dates one after each other
function outputDate(dates) {
  let message = ``;

  function format(date, separator = "-") {
    const parts = date.split(".");
    const year = parts[2];
    const month = parts[1];
    const day = parts[0];
    return new Date(`${year}${separator}${month}${separator}${day}`);
  }

  const startDate = format(dates[0]);
  const endDate = format(dates[1]);
  const diffInTime = endDate.getTime() - startDate.getTime();
  const diffInDays = Math.floor(diffInTime / (1000 * 3600 * 24));
  const diffInYears = Math.floor(diffInDays / 365);
  const diffInMonths = new Date(endDate - startDate).getMonth();

  // create the final message
  if (diffInYears > 0) {
    message += `${diffInYears} year${diffInYears > 1 ? `s` : ``}, `;
  }

  if (diffInMonths > 0) {
    message += `${diffInMonths} month${diffInMonths > 1 ? `s` : ``}, `;
  }

  message += `total ${diffInDays} days`;

  return message;
}