NpKnob

About

A small pure javascript library for creating rotating knobs. It was created while I had the idea to rebuild my BeatMachine.

Usage

Install by npm: npm install np-knob

You can import it in your project the next ways:

• the ES6 way: import NpKnob from 'np-knob';
• the node way: const NpKnob = require('np-knob');
• the old-skool way using the script tag

In you project create an element with an id. Then add the next code:

const knob1 = new NpKnob('your-id', options);

...and thats it. Now you can listen to the events it's fyering:

knob1.knob.addEventListener('knob-rotate', (evt) => {
    /**
     * Print the value of the button
     */
    console.log(evt.default.value);
});

Documentation

Option

• id: The id of the DOM-element
• options: Set of default options. This is an object with the following aatributes:
  • min: the minimum value of the knob
  • max: the maximum value of the knob
  • step: the step size in decimals.
    • step -1 is in 0.1 step-size
    • step 0 is in 1 step-size
    • step 1 is in 10 step-size
  • value: the start value of the knob

Methods

• obj: Returns the DOM-element of the corresponding knob
• getValue: Get the current value of the knob
• setValue: Set a new value to the knob

Events

When rotating the knob or clicking it to set the value an event is fired.

• knob-rotate: Parses the value of the knob

Also the created input can be used for eventlistening. You can do it like:

const knob1 = new NpKnob('your-id', options);
knob1.input.addEventlistener(event, callback);

Styling

NpKnob can easily be styled with css. Here's an example.

.npknob + input[type="number"] {
  display: none;
}

.npknob-wrapper {
  display: inline-block;
  height: 120px;
  margin: 1rem auto;
  position: relative;
  width: 120px;
}

.npknob {
  transition: transform .5s ease;
  background: transparent;
  border-color: #92c5c8;
  border-style: solid;
  border-radius: 50%;
  border-width: 6px;
  box-sizing: border-box;
  display: block;
  position: relative;
  width: 120px;
  height: 120px;
}

.npknob::after {
  content: '';
  background-color: #92c5c8;
  display: block;
  height: 40%;
  left: 50%;
  position: absolute;
  top: 0;
  transform: translateX(-50%);
  width: 6px;
}

.npknob.active {
  transition: none;
  border-color: #a3dde0;
  box-shadow: 0 0 5px 0 #a3dde0, inset 0 0 5px 0 #a3dde0;
}

.npknob.active::after {
  background-color: #a3dde0;
  box-shadow: 0 0 5px 0 #a3dde0, inset 0 0 5px 0 #a3dde0;
}