Frontend Assessment

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'],
];


const dayCounts = [
    31,
    28,
    31,
    30,
    31,
    30,
    31,
    31,
    30,
    31,
    30,
    31
];

// Receive string of dates one after each other
function outputDate(dates) {
    let leapDayCount = 0;

    let split = dates[0].split('.');
    const startDate = {
        day: parseInt(split[0]),
        month: parseInt(split[1]),
        year: parseInt(split[2])
    };

    split = dates[1].split('.');
    const endDate = {
        day: parseInt(split[0]),
        month: parseInt(split[1]),
        year: parseInt(split[2])
    };

    let i = startDate.year;

    // Skip starting year leap day check
    if (startDate.month > 2)
        i = startDate.year + 1;

    for (; i <= endDate.year; i++) {
        if (isLeapYear(i))
            leapDayCount++;
    }

    // Discard extra leap year if month is less than 2 (Feb)
    if (isLeapYear(endDate.year) && endDate.month <= 2)
        leapDayCount--;

    let totalDays = (endDate.year - startDate.year) * 365;

    totalDays += leapDayCount;
    totalDays = totalDays - getCumulativeDayCount(startDate.day, startDate.month);
    totalDays = totalDays + getCumulativeDayCount(endDate.day, endDate.month);

    const totalYears = parseInt(totalDays / 365);
    const totalMonths = parseInt((totalDays % 365) / 30);

    let yearString = '';
    let monthString = '';

    if (totalYears == 1)
        yearString = `${totalYears} year, `;
    else if (totalYears > 1)
        yearString = `${totalYears} years, `;

    if (totalDays <= 30)
        monthString = '';
    else if (totalMonths == 1)
        monthString = `${totalMonths} month, `;
    else if (totalMonths > 1)
        monthString = `${totalMonths} months, `;

    return `${yearString}${monthString}total ${totalDays} days`;
}

// Check leap year
function isLeapYear(year) {
    if ((year % 4 == 0 && year % 100 > 0) || (year % 400 == 0))
        return true;

    return false;
}

// Get day count upto specified month and day of a year.
function getCumulativeDayCount(day, month) {
    let count = 0;
    for (let i = 1; i < month; i++)
        count += dayCounts[i - 1];

    count += day;

    return count;
}