slider

a backbone + underscore custom control experiment

HTML

<script src="http://code.jquery.com/jquery-1.9.1.min.js"></script>
<body>
    <div class="label">Slider Demo</div>
    <div id="sliderContainer"></div>
</body>

CSS

BODY {
    margin: 20px;
}

DIV {
    margin: 0px;
}

#sliderContainer {
}
.label {
    font-family: Tahoma, Arial;
    font-size: 14px;
    font-weight: bold;
    padding: 4px 4px 6px 4px;
}
.slider {
    min-height: 25px;
    min-width: 100px;
    border-radius: 5px;
    background-color: #f6f6f6;
}
.sliderTrack {
    position: relative;
    top: 11px;
    margin: 0px 10px 0px 10px;
    height: 2px;
    border-radius: 2px;
    border: 1px solid #cec3c3;
    background-color: #cfcfcf;
}
.sliderThumbContainer {
    position: relative;
    top: -2px;
    width: 22px;
    height: 23px;
    cursor: pointer;
/* background-color: #cfcfcf; */
}
.sliderThumb {
    top: 0px;
    left: 0px;
    width: 12px;
    height: 20px;
    margin: 0 auto;
    border-radius: 5px;
    border: 1px solid #c3c3c3;
    background: #ccc;
    box-shadow: 0px 1px 3px rgba(0, 0, 0, 0.20);
}

JavaScript

/*
 * What does this do?
 *
 * It started out with me trying to find a reasonably good slider control for a web app. The app has 
 * a lot of UI that is built dynamically, where the DOM is constructed and styles are set directly via
 * javascript. I didn't like that and wanted to try out a template system like what backbone views do
 * with _. But there really is no model or collection here -- I could if I streched it all the way, but
 * that's not the goal here.
 *
 * What I ended up with separates the view and CSS from the logic of the actual control. And it turned
 * out to be quite similar to how most javascript templating systems work. The control, when instantiated,
 * creates a template with appropriate parameters filled in and then uses jQuery to contruct an element 
 * tree by using the template instance as the HTML input. This is the line that reads like,
 *
 *     _$el = $(_.template(_t, { id: id, width: (width || 100) })),
 *
 * The rest is straightforward. We get direct references to elements in this tree where we need to bind
 * event handlers or change properties later, again using jQuery. This is so that we aren't repeatedly
 * execution jQuery selectors which can get a bit slow if we're not careful.
 *
 * Backbone is also used to expose custom events from this control. This is not wired up yet, but will be 
 * soon.
 */
function slider(id, width) {

    _.extend(this, Backbone.Events);

    var _i = this,

        // todo - can we refactor to get _thumbWidth from element styles?
        _thumbWidth = 24,
        
        _slideRange = width - _thumbWidth, 

        // View template for control. Typically this would be outside the class, 
        // so it's reused between multiple instance of this control.
        // The id is bound as a paremeter in the template. There may be other parameters.
        //
        _t = '<div id="<%=id%>" class="slider" style="width:<%=width%>px;">' +
             '  <div id="<%=id%>_track"...