Javascript Date to string with ISO format (with timezone)

Question

I've been using MomentJS a lot but I'm starting a new project and I don't want to include this library since I play with dates only a couple of times.

So what I'm trying to do is to get the string representation of a date, in ISO-like format ('YYYY-MM-DDZHH:mm:ss' or 'YYYY-MM-DD HH:mm:ss'). I don't want it in UTC: I want it in a given timezone (that I can provide programatically).

E.g the representation for right now would be "2017-04-11 11:20:00" (French timezone - eq to "2017-04-11 09:22:00Z".)

I want native Javascript. I've been playing with toLocaleString with no success.

Thanks

[edit] In a perfect world, I'm looking for a function that takes a date format, a timezone, and return the string I want. Like:

function magicDateFormatter(format, tz) {
  /* ... */
}

var now = new Date();
console.log(magicDateFormatter('YYYY-MM-DD HH:mm:ss', 'Europe/Paris'));
// print "2017-04-11 11:20:00"

Answer 1

const dt = new Date().toLocaleString("sv-SE");

Answer 2

Something like this might work for you:

function formatDateWithZone(date, tz) {
    var s = date.toLocaleString('en-GB', { timeZone: tz });
    var a = s.split(/\D/);
    return a[2] + '-' + a[1] + '-' + a[0] + ' ' + a[4] + ':' + a[5] + ':' + a[6];
}

Usage:

formatDateWithZone(new Date(), 'Europe/Paris')  // "2017-04-12 03:37:59"

This will work in environments that have implemented time zone support via ECMA-402. The compatibility table here will show you which support them, by expanding the DateTimeFormat section, and looking at the row labeled accepts IANA timezone names.