difference between dates in javscript code example

Example 1: javascript difference between two dates in days

/* difference between date1 and date2 in days (date2 - date1) */
/* date1 and date 2 are already javascript date objects */
function dateDifference(date2, date1) {
    const _MS_PER_DAY = 1000 * 60 * 60 * 24;

    // Discard the time and time-zone information.
    const utc1 = Date.UTC(date1.getFullYear(), date1.getMonth(), date1.getDate());
    const utc2 = Date.UTC(date2.getFullYear(), date2.getMonth(), date2.getDate());

    return Math.floor((utc2 - utc1) / _MS_PER_DAY);
}

Example 2: javascript difference between two dates in days

const diffDays = (date, otherDate) => Math.ceil(Math.abs(date - otherDate) / (1000 * 60 * 60 * 24));

// Example
diffDays(new Date('2014-12-19'), new Date('2020-01-01'));   // 1839