let unix_timestamp = 1549312452
// Create a new JavaScript Date object based on the timestamp
// multiplied by 1000 so that the argument is in milliseconds, not seconds.
var date = new Date(unix_timestamp * 1000);
// Hours part from the timestamp
var hours = date.getHours();
// Minutes part from the timestamp
var minutes = "0" + date.getMinutes();
// Seconds part from the timestamp
var seconds = "0" + date.getSeconds();

// Will display time in 10:30:23 format
var formattedTime = hours + ':' + minutes.substr(-2) + ':' + seconds.substr(-2);

console.log(formattedTime);

For more information regarding the Date object, please refer to MDN or the ECMAScript 5 specification.

JavaScript works in milliseconds, so you'll first have to convert the UNIX timestamp from seconds to milliseconds.

var date = new Date(UNIX_Timestamp * 1000);
// Manipulate JavaScript Date object here...

Use:

var s = new Date(1504095567183).toLocaleDateString("en-US")
console.log(s)
// expected output "8/30/2017"  

and for time:

var s = new Date(1504095567183).toLocaleTimeString("en-US")
console.log(s)
// expected output "3:19:27 PM"

see Date.prototype.toLocaleDateString()

I'd think about using a library like momentjs.com, that makes this really simple:

Based on a Unix timestamp:

var timestamp = moment.unix(1293683278);
console.log( timestamp.format("HH/mm/ss") );

Based on a MySQL date string:

var now = moment("2010-10-10 12:03:15");
console.log( now.format("HH/mm/ss") );

shortest one-liner solution to format seconds as hh:mm:ss: variant:

console.log(new Date(1549312452 * 1000).toISOString().slice(0, 19).replace('T', ' '));
// "2019-02-04 20:34:12"

This works with PHP timestamps

var d = 1541415288860;
//var d =val.timestamp;

//NB: use + before variable name
var date = new Date(+d);

console.log(d);
console.log(date.toDateString());
console.log(date.getFullYear());
console.log(date.getMinutes());
console.log(date.getSeconds());
console.log(date.getHours());
console.log(date.toLocaleTimeString());

var d =val.timestamp;
var date=new Date(+d); //NB: use + before variable name

console.log(d);
console.log(date.toDateString());
console.log(date.getFullYear());
console.log(date.getMinutes());
console.log(date.getSeconds());
console.log(date.getHours());
console.log(date.toLocaleTimeString());

the methods above will generate this results

1541415288860
Mon Nov 05 2018 
2018 
54 
48 
13
1:54:48 PM

There's a bunch of methods that work perfectly with timestamps. Cant list them all

UNIX timestamp is number of seconds since 00:00:00 UTC on January 1, 1970 (according to Wikipedia).

Argument of Date object in Javascript is number of miliseconds since 00:00:00 UTC on January 1, 1970 (according to W3Schools Javascript documentation).

See code below for example:

    function tm(unix_tm) {
        var dt = new Date(unix_tm*1000);
        document.writeln(dt.getHours() + '/' + dt.getMinutes() + '/' + dt.getSeconds() + ' -- ' + dt + '<br>');

    }

tm(60);
tm(86400);

gives:

1/1/0 -- Thu Jan 01 1970 01:01:00 GMT+0100 (Central European Standard Time)
1/0/0 -- Fri Jan 02 1970 01:00:00 GMT+0100 (Central European Standard Time)

Shortest

(new Date(ts*1000)+'').slice(16,24)

let ts = 1549312452;
let time = (new Date(ts*1000)+'').slice(16,24);

console.log(time);

There are multiple ways to convert unix timestamp to time (HH/MM/SS)

1. Using new Date() - this is in-built in javascript
2. moment package - this is a famous node module, but this is going to deprecate.
3. dayjs package - this is one of the latest and fast growing node module

Using new Date()

const dateTimeStr = new Date(1504052527183).toLocaleString()
const result = (dateTimeStr.split(", ")[1]).split(":").join("/")
console.log(result)

Using moment

const moment = require('moment')
const timestampObj = moment.unix(1504052527183);
const result = timestampObj.format("HH/mm/ss")
console.log(result);

Using day.js

const dayjs = require('dayjs')
const result = dayjs(1504052527183).format("HH/mm/ss")
console.log(result);

you can check the timestamp to time conversion with an online time conversion tool

moment.js

convert timestamps to date string in js

https://momentjs.com/

moment().format('YYYY-MM-DD hh:mm:ss');
// "2020-01-10 11:55:43"

moment(1578478211000).format('YYYY-MM-DD hh:mm:ss');
// "2020-01-08 06:10:11"

Try this :

      new Date(1638525320* 1e3).toISOString()  //2021-12-03T09:55:20.000Z

Code below also provides 3-digit millisecs, ideal for console log prefixes:

const timeStrGet = date => {
    const milliSecsStr = date.getMilliseconds().toString().padStart(3, '0') ;
    return `${date.toLocaleTimeString('it-US')}.${milliSecsStr}`;
};

setInterval(() => console.log(timeStrGet(new Date())), 299);

The answer given by @Aron works, but it didn't work for me as I was trying to convert timestamp starting from 1980. So I made few changes as follows

function ConvertUnixTimeToDateForLeap(UNIX_Timestamp) {
    var dateObj = new Date(1980, 0, 1, 0, 0, 0, 0);
    dateObj.setSeconds(dateObj.getSeconds() + UNIX_Timestamp);
    return dateObj;  
}

document.body.innerHTML = 'TimeStamp : ' + ConvertUnixTimeToDateForLeap(1269700200);

So if you have a timestamp starting from another decade or so, just use this. It saved a lot of headache for me.

If Timestamp is a numeric integer string, it must be converted to integer number first:

<!DOCTYPE html>

<input type="text" id="Date_Timestamp" size="50" oninput='
document.getElementById("Date_Timestamp_Conversion").innerText = 
new Date(this.value) + " _ (Converted to Local Time) \n" +
new Date(this.value).toString() + " _ (Converted to Local Time) \n" +
new Date(this.value).toUTCString() + " _ (Converted to Universal Time, UTC, GMT, GMT+0, GMT-0) \n" +
Date.parse(this.value) + " _ (Timestamp _ The Date is first converted to Universal Time, then converted to Timestamp)\n" +
( isNaN(this.value) ? "Not a Number _ (Timestamp to Local Time)" : new Date(parseInt(this.value)) + " _ (Converted to Local Time)" ) + "\n" +
( isNaN(this.value) ? "Not a Number _ (Timestamp to Universal Time)" : new Date(parseInt(this.value)).toUTCString() + " _ (Converted to Universal Time)" ) + "\n" +
"";'>
<br>
<span id="Date_Timestamp_Conversion">(Type\Paste a "Date" or "Timestamp" in the input box above!)<br></span>
<br>
2021/03/19 = March 19 2021 _ ("Year/Month/Day" _ Supported)<br>
03/19/2021 = March 19 2021 _ ("Month/Day/Year" _ Supported)<br>
19/03/2021 = Invalid Date _ ("Day/Month/Year" _ Not Supported)<br>
<br>

<script>

d = new Date();
document.getElementById("Date_Timestamp").value =
d.getFullYear() + "/" + (d.getMonth() + 1) + "/" + d.getDate() + ", " + d.toLocaleTimeString([], {hour12:false, timeZoneName:"short"});

</script>

You can play around with the format (source):

const date = new Date(yourTimestamp).toLocaleDateString('de-DE', {
    weekday: 'long',
    day: '2-digit',
    month: 'long',
    year: 'numeric'
})

Result:

Sonntag, 01. Januar 2023