How to Make a Digital Clock with jQuery and CSS3

It all started last week when I saw this pretty dribbble shot. I immediately felt the urge to convert it into a working clock and share it with Tutorialzine's readers. If you'd like to learn how I made it, read on!

Update: The second part of this tutorial is now live! There we are adding support for setting alarms with HTML5 audio. Read it here.

The Markup

The clock doesn't need a lot of HTML. This is because a large part of it, like the names of the weekdays and the code for the digits, is generated dynamically. Here is the markup that you need to have on your page to use the clock:

index.html

<div id="clock" class="light">
    <div class="display">
        <div class="weekdays"></div>
        <div class="ampm"></div>
        <div class="alarm"></div>
        <div class="digits"></div>
    </div>
</div>

The main element, the #clock div, contains the .display, which in turn holds the list of weekdays, AM/PM label the alarm icon and the time. And here is the generated markup for one of the digits:

<div class="zero">
    <span class="d1"></span>
    <span class="d2"></span>
    <span class="d3"></span>
    <span class="d4"></span>
    <span class="d5"></span>
    <span class="d6"></span>
    <span class="d7"></span>
</div>

The .digits element will contain 6 of these divs with spans, one for each digit of the time. As you can see from the fragment above, these divs get a class name from zero to nine (more on that in a second), and contain seven span elements with unique classes. These spans are the segments of the digits, like in the digital clocks of old:

They are styled entirely with CSS and are set to opacity:0 by default. The class assigned to their parent div is what makes them visible. Here is the CSS for the zero:

assets/css/styles.css

/* 0 */

#clock .digits div.zero .d1,
#clock .digits div.zero .d3,
#clock .digits div.zero .d4,
#clock .digits div.zero .d5,
#clock .digits div.zero .d6,
#clock .digits div.zero .d7{
    opacity:1;
}

All segments are visible, except for the middle one (otherwise it would be an 8). I have added a CSS3 transition property to all these spans, which animates the opacity when switching between numbers.

There is a lot of other CSS in the stylesheet, but I will not be presenting it here. I believe the best way to learn how the CSS works is by inspecting the live-working code of the demo in Firebug, Chrome's Inspector or the developer tools of your browser of choice.

The jQuery Code

To make the clock work, we will have to use jQuery to generate the markup for each of the digits, and set a timer to update the classes every second. To make our lives easier, we will use the moment.js library (quick tip) to compensate for the lacking JavaScript native date and time functions.

assets/js/script.js

$(function(){

    // Cache some selectors

    var clock = $('#clock'),
        alarm = clock.find('.alarm'),
        ampm = clock.find('.ampm');

    // Map digits to their names (this will be an array)
    var digit_to_name = 'zero one two three four five six seven eight nine'.split(' ');

    // This object will hold the digit elements
    var digits = {};

    // Positions for the hours, minutes, and seconds
    var positions = [
        'h1', 'h2', ':', 'm1', 'm2', ':', 's1', 's2'
    ];

    // Generate the digits with the needed markup,
    // and add them to the clock

    var digit_holder = clock.find('.digits');

    $.each(positions, function(){

        if(this == ':'){
            digit_holder.append('<div class="dots">');
        }
        else{

            var pos = $('<div>');

            for(var i=1; i<8; i++){
                pos.append('<span class="d' + i + '">');
            }

            // Set the digits as key:value pairs in the digits object
            digits[this] = pos;

            // Add the digit elements to the page
            digit_holder.append(pos);
        }

    });

    // Add the weekday names

    var weekday_names = 'MON TUE WED THU FRI SAT SUN'.split(' '),
        weekday_holder = clock.find('.weekdays');

    $.each(weekday_names, function(){
        weekday_holder.append('<span>' + this + '</span>');
    });

    var weekdays = clock.find('.weekdays span');

    // Run a timer every second and update the clock

    (function update_time(){

        // Use moment.js to output the current time as a string
        // hh is for the hours in 12-hour format,
        // mm - minutes, ss-seconds (all with leading zeroes),
        // d is for day of week and A is for AM/PM

        var now = moment().format("hhmmssdA");

        digits.h1.attr('class', digit_to_name[now[0]]);
        digits.h2.attr('class', digit_to_name[now[1]]);
        digits.m1.attr('class', digit_to_name[now[2]]);
        digits.m2.attr('class', digit_to_name[now[3]]);
        digits.s1.attr('class', digit_to_name[now[4]]);
        digits.s2.attr('class', digit_to_name[now[5]]);

        // The library returns Sunday as the first day of the week.
        // Stupid, I know. Lets shift all the days one position down, 
        // and make Sunday last

        var dow = now[6];
        dow--;

        // Sunday!
        if(dow < 0){
            // Make it last
            dow = 6;
        }

        // Mark the active day of the week
        weekdays.removeClass('active').eq(dow).addClass('active');

        // Set the am/pm text:
        ampm.text(now[7]+now[8]);

        // Schedule this function to be run again in 1 sec
        setTimeout(update_time, 1000);

    })();

    // Switch the theme

    $('a.button').click(function(){
        clock.toggleClass('light dark');
    });

});

The most important piece of code here is the update_time function. Inside it, we get the current time as a string, and use it to fill in the elements of the clock and to set the correct classes to the digits.

With this our digital clock is ready! Check the next part, where we adding support for setting alarms and playing them back with HTML5 audio.