Ever needed to show something on-screen as a percentage / bar in javascript? Yes, it has been done a countless number of times before. Sometimes, even in mootools. But we like adding our own functions to the dci_core.js mini library whenever possible. So … here is a very easy and good-looking way of doing it (well, subject of what background images you can come up with, of course). The idea is simple: have a container element with a background image that is offset to outside the element’s boundaries via the background-position CSS property. As the percentage is being calculated, the background image is bring brought into view.

Our progress images look like this:

200px wide, so each percent is represented by 2px, something that is reflected in the script below. Here is the target element, styled as per our CSS:

Some more examples of various options for the progress bar, settings are contained within the actual elements:

Here’s the relevant CSS:

.progress {
    width: 200px;
    border: 1px solid #000;
    background-color: #d81e05;
    background-image: url(/gallery/img/progress.gif);
    background-repeat: no-repeat;
    background-position: -210px 0;
    height: 16px;
    line-height: 1;
    color: #F4F4F4;
    font-weight: bold;
    margin-bottom: 4px;
}
.progress2 {
    width: 202px;
    border: 1px solid #000;
    background-color: #555;
    background-image: url(/images/progressbar-orange.gif);
    background-repeat: no-repeat;
    background-position: -210px 0px;
    height: 21px;
    color: #000;
    font-weight: bold;
    margin-left: 1px;
}

The actual div and html:

<div class="progress" id="someid"></div>

Some more examples of various options for the progress bar, settings are contained within the actual elements:
<a href="#" class="barbar" data-data="{count:23,total:26,message:'loaded...',className:'progress2'}">23 of 26, "images loaded..." with cubic tween, class: progress2</a>
<a href="#" class="barbar" data-data="{count:4,total:5,message:'completed',tween:false}">4 of 5, 'completed', no tween</a>
<a href="#" class="barbar" data-data="{count:14,total:80,message:'Questions'}">14 of 80, 'Questions', cubic tween</a>

Here’s how we extend the element in mootools and call the methods we need:

Element.implement({
    showProgress: function(options) {
        options = $merge({
            count: 0,
            total: 10,
            message: "",
            className: "progress", // default css class
            backgroundPosition: 200, // start pos
            tween: true // animate or static
        }, options);

        // calculate % of progress
        var percent = options.total / 100, donePercent = (options.count / percent).round(), BGoffset = options.backgroundPosition - (donePercent*2).round();

        // set inline message
        this.set({
            styles: {
                "background-position": "-" + options.backgroundPosition + "px"
            },
            html: "  " + options.count + " of " + options.total + " " + options.message + " ("+donePercent+"%)",
            "class": options.className
        });

        if (options.tween)
            new Fx.Tween(this, {
                duration: 500,
                transition: Fx.Transitions.Cubic.easeIn
            }).start("background-position", "-" + BGoffset);
        else
            this.setStyle("background-position", "-" + BGoffset + "px");

        this.store("percent", donePercent); // element storage, use element.retrieve("data-percent") to get current progress.
        return this;
    }
}); // end extending elements

// apply initial state
$("someid").showProgress({count:3,total:10}); 

// bind the links to change the bar graph to real time data.
$$("a.barbar").addEvents({
    click: function(e) {
        new Event(e).stop();
        $("someid").showProgress(JSON.decode(this.get("data-data")));
    }
});

// show / read percent from element storage
$("fetchPercent").addEvent("mouseenter", function(e) {
    this.tooltip("This bar at " + $("someid").retrieve("percent") + "%");
});

That’s it, I hope it helps you. In an ideal world, this could be refactored into a mootools class but who has the time…