Convert seconds to HH-MM-SS with JavaScript?

Updated (2020):

Please use @Frank's one line solution:

new Date(SECONDS * 1000).toISOString().substring(11, 16)

If SECONDS<3600 and if you want to show only MM:SS then use below code:

new Date(SECONDS * 1000).toISOString().substring(14, 19)

It is by far the best solution.

Old answer:

Use the Moment.js library.

I don't think any built-in feature of the standard Date object will do this for you in a way that's more convenient than just doing the math yourself.

hours = Math.floor(totalSeconds / 3600);
totalSeconds %= 3600;
minutes = Math.floor(totalSeconds / 60);
seconds = totalSeconds % 60;

Example:

let totalSeconds = 28565;
let hours = Math.floor(totalSeconds / 3600);
totalSeconds %= 3600;
let minutes = Math.floor(totalSeconds / 60);
let seconds = totalSeconds % 60;

console.log("hours: " + hours);
console.log("minutes: " + minutes);
console.log("seconds: " + seconds);

// If you want strings with leading zeroes:
minutes = String(minutes).padStart(2, "0");
hours = String(hours).padStart(2, "0");
seconds = String(seconds).padStart(2, "0");
console.log(hours + ":" + minutes + ":" + seconds);

You can manage to do this without any external JavaScript library with the help of JavaScript Date method like following:

var date = new Date(null);
date.setSeconds(SECONDS); // specify value for SECONDS here
var result = date.toISOString().substr(11, 8);

Or, as per @Frank's comment; a one liner:

new Date(SECONDS * 1000).toISOString().substr(11, 8);