how to get difference between two date and time in javascript code example

Example 1: javascript calculate time

console.time("timer");   //start time with name = timer
console.timeEnd("timer"); //end timer and log time difference

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