Nsryjdtyk

I'm new to JavaScript and I'm trying to write a code which calculates the time elapsed from the time a user logged in to the current time.

Here is my code:-

function markPresent() {

    window.markDate = new Date();

    $(document).ready(function() {

        $("div.absent").toggleClass("present");

    });

    updateClock();

}



function updateClock() {    

    var markMinutes = markDate.getMinutes();

    var markSeconds = markDate.getSeconds();



    var currDate = new Date();

    var currMinutes = currDate.getMinutes();

    var currSeconds = currDate.getSeconds();

    var minutes = currMinutes - markMinutes;

    if(minutes < 0) { minutes += 60; }

    var seconds = currSeconds - markSeconds;

    if(seconds < 0) { seconds += 60; }



    if(minutes < 10) { minutes = "0" + minutes; }

    if(seconds < 10) { seconds = "0" + seconds; }



    var hours = 0;

    if(minutes == 59 && seconds == 59) { hours++; }

    if(hours < 10) { hours = "0" + hours; }



    var timeElapsed = hours+':'+minutes+':'+seconds;

    document.getElementById("timer").innerHTML = timeElapsed;

    setTimeout(function() {updateClock()}, 1000);

}

The output is correct upto 00:59:59 but after that that O/P is:

00:59:59
01:59:59
01:59:00
01:59:01
.
.
.
.
01:59:59
01:00:00

How can I solve this and is there a more efficient way I can do this?
Thank you.

There's too much going on here.

An easier way would just be to compare markDate to the current date each time and reformat.

See Demo: http://jsfiddle.net/7e4psrzu/

function markPresent() {

    window.markDate = new Date();

    $(document).ready(function() {

        $("div.absent").toggleClass("present");

    });

    updateClock();

}



function updateClock() {  

    var currDate = new Date();

    var diff = currDate - markDate;

    document.getElementById("timer").innerHTML = format(diff/1000);

    setTimeout(function() {updateClock()}, 1000);

}



function format(seconds)

{

var numhours = parseInt(Math.floor(((seconds % 31536000) % 86400) / 3600),10);

var numminutes = parseInt(Math.floor((((seconds % 31536000) % 86400) % 3600) / 60),10);

var numseconds = parseInt((((seconds % 31536000) % 86400) % 3600) % 60,10);

    return ((numhours<10) ? "0" + numhours : numhours)

    + ":" + ((numminutes<10) ? "0" + numminutes : numminutes)

    + ":" + ((numseconds<10) ? "0" + numseconds : numseconds);

}



markPresent();

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.0/jquery.min.js"></script>

<div id="timer"></div>

No offence, but this is massively over-enginered. Simply store the start time when the script first runs, then subtract that from the current time every time your timer fires.

There are plenty of tutorials on converting ms into a readable timestamp, so that doesn't need to be covered here.

    var start = Date.now();

    

    setInterval(function() {

      document.getElementById('difference').innerHTML = Date.now() - start;

    

      // the difference will be in ms

    }, 1000);

<div id="difference"></div>

Here is a solution I just made for my use case. I find it is quite readable. The basic premise is to simply subtract the timestamp from the current timestamp, and then divide it by the correct units:

const showElapsedTime = (timestamp) => {

    if (typeof timestamp !== 'number') return 'NaN'        



    const SECOND = 1000

    const MINUTE = 1000 * 60

    const HOUR = 1000 * 60 * 60

    const DAY = 1000 * 60 * 60 * 24

    const MONTH = 1000 * 60 * 60 * 24 * 30

    const YEAR = 1000 * 60 * 60 * 24 * 30 * 12

    

    // const elapsed = ((new Date()).valueOf() - timestamp)

    const elapsed = 1541309742360 - timestamp

    

    if (elapsed <= MINUTE) return `${Math.round(elapsed / SECOND)}s`

    if (elapsed <= HOUR) return `${Math.round(elapsed / MINUTE)}m`

    if (elapsed <= DAY) return `${Math.round(elapsed / HOUR)}h`

    if (elapsed <= MONTH) return `${Math.round(elapsed / DAY)}d`

    if (elapsed <= YEAR) return `${Math.round(elapsed / MONTH)}mo`

    return `${Math.round(elapsed / YEAR)}y`

}

      

const createdAt = 1541301301000



console.log(showElapsedTime(createdAt + 5000000))

console.log(showElapsedTime(createdAt))

console.log(showElapsedTime(createdAt - 500000000))

For example, if 3000 milliseconds elapsed, then 3000 is greater than SECONDS (1000) but less than MINUTES (60,000), so this function will divide 3000 by 1000 and return 3s for 3 seconds elapsed.

If you need timestamps in seconds instead of milliseconds, change all instances of 1000 to 1 (which effectively multiplies everything by 1000 to go from milliseconds to seconds (ie: because 1000ms per 1s).

Here are the scaling units in more DRY form:

const SECOND = 1000

const MINUTE = SECOND * 60

const HOUR = MINUTE * 60

const DAY = HOUR * 24

const MONTH = DAY * 30

const YEAR = MONTH * 12

var hours = 0;

if(minutes == 59 && seconds == 59) 

{ 

    hours = hours + 1; 

    minutes = '00'; 

    seconds == '00';

}

I would use the getTime() method, subtract the time and then convert the result into hh:mm:ss.mmm format.