jQuery Knob

Knob represents a jQuery plugin with round shape which displays a draggable indicator within a range of values. Knob can be used in a table or matrix to show the relative value of a field in a range of values in the data region, for example, as a KPI. It supports HTML5, SVG and VML rendering. Knob.js makes it easy to include multitouch virtual knobs in your web app. The primary features of Knob Plugin:

  • Canvas based ; no png or jpg sprites.
  • Touch, mouse and mousewheel, keyboard events implemented.
  • Downward compatible ; overloads an input element.
  • Minimum/maximum angle & value constraints.
  • Figuring out the position and angle of the indicator dot.
  • Doing the math for displaying custom rendered knobs using image sprites.

Live Demo

× Disable display input

× 'cursor' mode

× Display previous value

× Angle offset

× Angle offset and arc

× 4-digit, step 0.1

× Overloaded 'draw' method

× Responsive

Current div width is 30% of window width.
Knob width is 80% of current div.
Knob width is 80% of 30% of window width.
Test resizing window.

× Superpose (clock)

× Readonly

× Dynamic

× Infinite || iPod click wheel

0

How to Use

1. CSS

Add the css below to your html page

<style>
    body {
        padding: 0;
        margin: 0px 50px;
        font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;
        font-weight: 300;
        text-rendering: optimizelegibility;
    }

    p {
        font-size: 30px;
        line-height: 30px
    }

    div.demo {
        text-align: center;
        width: 280px;
        float: left
    }

    div.demo>p {
        font-size: 20px
    }
</style>

2. HTML

Create a container where you want to render knob

<div class="demo">
    <p>&#215; Disable display input</p>
    <input class="knob" data-width="100" data-displayInput=false value="35">
</div>

<div class="demo">
    <p>&#215; 'cursor' mode</p>
    <input class="knob" data-width="150" data-cursor=true data-fgColor="#222222" data-thickness=.3 value="29">
</div>

<div class="demo">
    <p>&#215; Display previous value</p>
    <input class="knob" data-width="200" data-min="-100" data-displayPrevious=true value="44">
</div>
<div style="clear:both"></div>

<div class="demo">
    <p>&#215; Angle offset</p>
    <input class="knob" data-angleOffset=90 data-linecap=round value="35">
</div>

<div class="demo">
    <p>&#215; Angle offset and arc</p>
    <input class="knob" data-angleOffset=-125 data-angleArc=250 data-fgColor="#66EE66" data-rotation="anticlockwise"
        value="35">
</div>

<div class="demo">
    <p>&#215; 4-digit, step 0.1</p>
    <input class="knob" data-min="-10000" data-displayPrevious=true data-max="10000" data-step=".1" value="0">
</div>

<div style="clear:both"></div>

<div>
    <p style="font-size: 20px">&#215; Overloaded 'draw' method</p>
</div>

<div>
    <div class="demo" style="color:#FFF;">
        <input class="knob" data-width="75" data-displayPrevious=true data-fgColor="#ffec03" data-skin="tron"
            data-cursor=true value="75" data-thickness=".2">
    </div>
    <div class="demo" style="color:#FFF;">
        <input class="knob" data-width="150" data-displayPrevious=true data-fgColor="#ffec03" data-skin="tron"
            data-thickness=".2" value="75">
    </div>
    <div class="demo" style="color:#FFF;">
        <input class="knob" data-width="150" data-angleOffset="180" data-fgColor="#C0ffff" data-skin="tron"
            data-thickness=".1" value="35">
    </div>
</div>

<div style="clear:both"></div>

<div class="demo" style="width:100%">
    <p>&#215; Responsive</p>
    <div style="width: 30%; border: 3px dashed; margin-bottom: 20px">
        <i>
            Current div width is 30% of window width.<br>
            Knob width is 80% of current div.<br>
            Knob width is 80% of 30% of window width.<br>
            Test resizing window.
        </i>
        <br>
        <br>
        <input class="knob" data-width="80%" value="35">
    </div>
</div>
<div style="clear:both"></div>
<script>
    function clock() {
        var $s = jQuery(".second"),
            $m = jQuery(".minute"),
            $h = jQuery(".hour");
        d = new Date(),
            s = d.getSeconds(),
            m = d.getMinutes(),
            h = d.getHours();
        $s.val(s).trigger("change");
        $m.val(m).trigger("change");
        $h.val(h).trigger("change");
        setTimeout("clock()", 1000);
    }
    clock();
</script>
<div class="demo" style="color:#EEE;background:#222;height:420px;width:100%">
    <p>&#215; Superpose (clock)</p>
    <div style="position:relative;width:350px;margin:auto">
        <div style="position:absolute;left:10px;top:10px">
            <input class="knob hour" data-min="0" data-max="24" data-bgColor="#333" data-fgColor="#ffec03"
                data-displayInput=false data-width="300" data-height="300" data-thickness=".3">
        </div>
        <div style="position:absolute;left:60px;top:60px">
            <input class="knob minute" data-min="0" data-max="60" data-bgColor="#333" data-displayInput=false
                data-width="200" data-height="200" data-thickness=".45">
        </div>
        <div style="position:absolute;left:110px;top:110px">
            <input class="knob second" data-min="0" data-max="60" data-bgColor="#333" data-fgColor="rgb(127, 255, 0)"
                data-displayInput=false data-width="100" data-height="100" data-thickness=".3">
        </div>
    </div>
</div>
<div style="clear:both"></div>
<div class="demo">
    <p>&#215; Readonly</p>
    <input class="knob" data-fgColor="chartreuse" data-thickness=".4" readonly value="22">
</div>
<div class="demo">
    <p>&#215; Dynamic</p>

    <input type="button" onclick="jQuery('.knob-dyn').knob();" value="knobify!">
    <input type="text" class="knob-dyn" data-width="200" data-cursor=true value="56">

    <input type="button" onclick="jQuery('.knob-dyn2').knob();" value="knobify!">
    <input type="text" class="knob-dyn2" data-width="50" data-thickness=".4" value="56">
</div>
<div class="demo" style="height:440px;width:300px">
    <p>&#215; Infinite || iPod click wheel</p>
    <div style="float:left;width:180px;height:320px;padding:20px;background-color:#EEEEEE;text-align:center;">

        <input class="infinite" value="0" data-width="150" data-thickness=".5" data-fgColor="#AAAAAA"
            data-bgColor="#FFFFFF" data-displayInput="false" data-cursor=true>
    </div>
    <div style="float:left;margin-top:200px;">
        <div class="ival" style="width:80px;text-align:center;font-size:50px;color:#AAA">0</div>
        <div class="idir" style="width:80px;text-align:center;font-size:50px;"></div>
    </div>
</div>
<div style="clear:both"></div>

3. Javascript

Load jQuery library together with the Knob library into your code

<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.9.0/jquery.min.js"></script>
<script src="jquery.knob.min.js"></script>
<script>
    $(function ($) {

        $(".knob").knob({
            change: function (value) {
                //console.log("change : " + value);
            },
            release: function (value) {
                //console.log(this.$.attr('value'));
                console.log("release : " + value);
            },
            cancel: function () {
                console.log("cancel : ", this);
            },
            /*format : function (value) {
             return value + '%';
             },*/
            draw: function () {

                // "tron" case
                if (this.$.data('skin') == 'tron') {

                    this.cursorExt = 0.3;

                    var a = this.arc(this.cv) // Arc
                        ,
                        pa // Previous arc
                        , r = 1;

                    this.g.lineWidth = this.lineWidth;

                    if (this.o.displayPrevious) {
                        pa = this.arc(this.v);
                        this.g.beginPath();
                        this.g.strokeStyle = this.pColor;
                        this.g.arc(this.xy, this.xy, this.radius - this.lineWidth, pa.s, pa.e, pa
                            .d);
                        this.g.stroke();
                    }

                    this.g.beginPath();
                    this.g.strokeStyle = r ? this.o.fgColor : this.fgColor;
                    this.g.arc(this.xy, this.xy, this.radius - this.lineWidth, a.s, a.e, a.d);
                    this.g.stroke();

                    this.g.lineWidth = 2;
                    this.g.beginPath();
                    this.g.strokeStyle = this.o.fgColor;
                    this.g.arc(this.xy, this.xy, this.radius - this.lineWidth + 1 + this.lineWidth *
                        2 / 3, 0, 2 * Math.PI, false);
                    this.g.stroke();

                    return false;
                }
            }
        });

        // Example of infinite knob, iPod click wheel
        var v, up = 0,
            down = 0,
            i = 0,
            $idir = $("div.idir"),
            $ival = $("div.ival"),
            incr = function () {
                i++;
                $idir.show().html("+").fadeOut();
                $ival.html(i);
            },
            decr = function () {
                i--;
                $idir.show().html("-").fadeOut();
                $ival.html(i);
            };
        $("input.infinite").knob({
            min: 0,
            max: 20,
            stopper: false,
            change: function () {
                if (v > this.cv) {
                    if (up) {
                        decr();
                        up = 0;
                    } else {
                        up = 1;
                        down = 0;
                    }
                } else {
                    if (v < this.cv) {
                        if (down) {
                            incr();
                            down = 0;
                        } else {
                            down = 1;
                            up = 0;
                        }
                    }
                }
                v = this.cv;
            }
        });
    });
</script>

Source Code

Download

For more Advanced Usages, please check the demo page or visit the official website.

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