javascript get number of days between two dates

function dateDiffInDays(date1, date2) {
    // round to the nearest whole number
    return Math.round((date2-date1)/(1000*60*60*24));
}
var daysDiff=dateDiffInDays(new Date('December 21, 2019 03:24:00'), new Date('December 25, 2019 03:24:00')); //4 days till XMASconst 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