ok lets say we have a website that need a realtime time;

example :

<div id="updatetime">21:12:52</div>

each seconds update hours:m:second.

what i have in minds using the interval function to do long pool and add the sec +1 if to 60 then add + 1 to m and same as hours. but is there a function already solving this problem?

how do you make this 21:12:52 a moving real clock with javascript that updates each seconds?

i have search google, stackoverflow, many of them tells us how to make the current real time datetime from javascript. but none from an existing time. if there is please do insert the link.

ok lets say we have a website that need a realtime time;

example :

<div id="updatetime">21:12:52</div>

each seconds update hours:m:second.

what i have in minds using the interval function to do long pool and add the sec +1 if to 60 then add + 1 to m and same as hours. but is there a function already solving this problem?

how do you make this 21:12:52 a moving real clock with javascript that updates each seconds?

i have search google, stackoverflow, many of them tells us how to make the current real time datetime from javascript. but none from an existing time. if there is please do insert the link.

• javascript

• 1 What do you mean a existing time? – epascarello Commented Jun 7, 2012 at 11:51
• 21:12:52(existing time) to 21:12:53 each seconds add the time to the div – Adam Ramadhan Commented Jun 7, 2012 at 11:54
• Take a look to this TimeSpan class: codeproject.com/Articles/62852/… – Adriano Repetti Commented Jun 7, 2012 at 11:57
• existing time means whatever is set on the user's computer? – epascarello Commented Jun 7, 2012 at 12:01
• existing time means whatever is set on the div, sorry for the ambiguty, i want the div to be a live clock – Adam Ramadhan Commented Jun 7, 2012 at 12:08

5 Answers 5

It can be as easy as this:

setInterval(function(){
    document.getElementById("updatetime").innerHTML = (new Date()).toLocaleTimeString();
}, 1000);

Or use the other Date methods to fine-tune your output.

Update

I only now realized that OP was asking not about incrementing an element with the current time but with a predetermined time.

That's less trivial, but here is a solution that should fit the original question:

function increment_time_element(element, delay) {
    var interval, last,
        time_pattern = /(\d+):(\d+):(\d+)/,
        start = element.innerHTML.match(time_pattern),
        then = new Date;

    then.setHours  (parseInt(start[1], 10) || 0);
    then.setMinutes(parseInt(start[2], 10) || 0);
    then.setSeconds(parseInt(start[3], 10) || 0);

    function now() {
        return Date.now ? Date.now() : (new Date).getTime();
    }

    last = now();

    interval = setInterval(function () {
        var current = now();
        // correct for any interval drift by using actual difference
        then.setTime(then.getTime() + current - last)
        last = current;
        element.innerHTML = then.toString().match(time_pattern)[0];
    }, delay || 1000);

    return {cancel: function() { clearInterval(interval) }};
}

// Usage:
var incrementing_time =
    increment_time_element(document.getElementById("updatetime"));

// Then, if you want to cancel:
incrementing_time.cancel();

If you don't need a very high fidelity, you can use this way:

​var container  = document.getElementById("updatetime").firstChild;
var values = container.nodeValue.split(":");

// Because there is only a datetime specified, I assume is the current date
var now = new Date();
var time = new Date(now.getFullYear(), now.getMonth(), now.getDate(),
                    values[0], values[1], values​[2]).getTime();

setInterval(function() {
    time += 1000;
    var date = new Date(time);
    var values = [date.getHours(), date.getMinutes(), date.getSeconds()];

    for (var i = 0; i < 3; i++)
        if (values[i] < 10)
            values[i] = "0" + values[i];

    container.nodeValue = values.join(":");
}, 1000);

If you want to be more in sync with the current computer clock, then I suggest to you to use setTimeout and adjust the delay argument with the proper elapsed time.

Update: due the comments, it seems the elements to update are not only one and multiple, and the code is using jQuery. Here an approach that works for multiple elements using class to identify them:

var containers  = $(".updatetime");
var times = [];
var now = new Date();

containers.each(function(index, node) {
    var values = $(node).text().split(":");

    times[index] = new Date(
        now.getFullYear(), now.getMonth(), now.getDate(),
        values[0], values[1], values[2]).getTime();
});

setInterval(function() {
    containers.each(function(index, node) {
        times[index] += 1000;

        var date = new Date(times[index]);
        var values = [date.getHours(), date.getMinutes(), date.getSeconds()];

        for (var i = 0; i < 3; i++)
            if (values[i] < 10)
                values[i] = "0" + values[i];

        $(node).text(values.join(":"));
    });

}, 1000);

If your after a realtime clock that ticks along, take a look at the code I used when I created a "flip clock". I split each digit into a seperate individual digit to use for graphic placement within the clock, but if you strip it down you will have just text that updates.

Javascript Flip Clock

using HTML canvas

code:

var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");
var radius = canvas.height / 2;
ctx.translate(radius, radius);
radius = radius * 0.90
setInterval(drawClock, 1000);

function drawClock() {
  drawFace(ctx, radius);
  drawNumbers(ctx, radius);
  drawTime(ctx, radius);
}

function drawFace(ctx, radius) {
  var grad;
  ctx.beginPath();
  ctx.arc(0, 0, radius, 0, 2 * Math.PI);
  ctx.fillStyle = 'white';
  ctx.fill();
  grad = ctx.createRadialGradient(0, 0, radius * 0.95, 0, 0, radius * 1.05);
  grad.addColorStop(0, '#333');
  grad.addColorStop(0.5, 'white');
  grad.addColorStop(1, '#333');
  ctx.strokeStyle = grad;
  ctx.lineWidth = radius * 0.1;
  ctx.stroke();
  ctx.beginPath();
  ctx.arc(0, 0, radius * 0.1, 0, 2 * Math.PI);
  ctx.fillStyle = '#333';
  ctx.fill();
}

function drawNumbers(ctx, radius) {
  var ang;
  var num;
  ctx.font = radius * 0.15 + "px arial";
  ctx.textBaseline = "middle";
  ctx.textAlign = "center";
  for (num = 1; num < 13; num++) {
    ang = num * Math.PI / 6;
    ctx.rotate(ang);
    ctx.translate(0, -radius * 0.85);
    ctx.rotate(-ang);
    ctx.fillText(num.toString(), 0, 0);
    ctx.rotate(ang);
    ctx.translate(0, radius * 0.85);
    ctx.rotate(-ang);
  }
}

function drawTime(ctx, radius) {
  var now = new Date();
  var hour = now.getHours();
  var minute = now.getMinutes();
  var second = now.getSeconds();
  //hour
  hour = hour % 12;
  hour = (hour * Math.PI / 6) +
    (minute * Math.PI / (6 * 60)) +
    (second * Math.PI / (360 * 60));
  drawHand(ctx, hour, radius * 0.5, radius * 0.07);
  //minute
  minute = (minute * Math.PI / 30) + (second * Math.PI / (30 * 60));
  drawHand(ctx, minute, radius * 0.8, radius * 0.07);
  // second
  second = (second * Math.PI / 30);
  drawHand(ctx, second, radius * 0.9, radius * 0.02);
}

function drawHand(ctx, pos, length, width) {
  ctx.beginPath();
  ctx.lineWidth = width;
  ctx.lineCap = "round";
  ctx.moveTo(0, 0);
  ctx.rotate(pos);
  ctx.lineTo(0, -length);
  ctx.stroke();
  ctx.rotate(-pos);
}

<canvas id="canvas" width="400" height="400" style="background-color:#333">
</canvas>

you can do it with below code

<!DOCTYPE html>
<html>
<head>
<script>
function startTime() {
    var today = new Date();
    var h = today.getHours();
    var m = today.getMinutes();
    var s = today.getSeconds();
    m = checkTime(m);
    s = checkTime(s);
    document.getElementById('txt').innerHTML =
    h + ":" + m + ":" + s;
    var t = setTimeout(startTime, 500);
}
function checkTime(i) {
    if (i < 10) {i = "0" + i};  // add zero in front of numbers < 10
    return i;
}
</script>
</head>

<body onload="startTime()">

<div id="txt"></div>

</body>
</html>