Convert a Unix timestamp to time in JavaScript

Question

I am storing time in a MySQL database as a Unix timestamp and that gets sent to some JavaScript code. How would I get just the time out of it?

For example, in HH/MM/

Answer 1

Modern Solution (for 2020)

In the new world, we should be moving towards the standard Intl JavaScript object, that has a handy DateTimeFormat constructor with .format() method:

function format_time(s) {
  const dtFormat = new Intl.DateTimeFormat('en-GB', {
    timeStyle: 'medium',
    timeZone: 'UTC'
  });
  
  return dtFormat.format(new Date(s * 1e3));
}

console.log( format_time(12345) );  // "03:25:45"

---

Eternal Solution

But to be 100% compatible with all legacy JavaScript engines, here is the shortest one-liner solution to format seconds as hh:mm:ss:

function format_time(s) {
  return new Date(s * 1e3).toISOString().slice(-13, -5);
}

console.log( format_time(12345) );  // "03:25:45"

Method Date.prototype.toISOString() returns time in simplified extended ISO 8601 format, which is always 24 or 27 characters long (i.e. YYYY-MM-DDTHH:mm:ss.sssZ or ±YYYYYY-MM-DDTHH:mm:ss.sssZ respectively). The timezone is always zero UTC offset.

This solution does not require any third-party libraries and is supported in all browsers and JavaScript engines.