How to calculate date difference in JavaScript?

Question

I want to calculate date difference in days, hours, minutes, seconds, milliseconds, nanoseconds. How can I do it?

Answer 1

based on javascript runtime prototype implementation you can use simple arithmetic to subtract dates as in bellow

var sep = new Date(2020, 07, 31, 23, 59, 59);
var today = new Date();
var diffD = Math.floor((sep - today) / (1000 * 60 * 60 * 24));
console.log('Day Diff: '+diffD);

the difference return answer as milliseconds, then you have to convert it by division:

• by 1000 to convert to second
• by 1000×60 convert to minute
• by 1000×60×60 convert to hour
• by 1000×60×60×24 convert to day