lfo-for-modv/src/lfo.js

LFOs in JavaScript

// Copyright (c) 2017 Guillaume Bauer

// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the 'Software'), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:

// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.

// THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.

// GitHub: http://github.com/TheTeapot418/LFO.js

class LFO {
  constructor(param = {}) {
    this.startTime = new Date().getTime();
    this.freq = 1;
    this.amplitude = 2;
    this.waveform = null;
    this.set(param);
  }

  set(param = {}) {
    this.freq = param.freq || this.freq;
    this.amplitude = param.amplitude || this.amplitude;

    switch (param.waveform) {
      case 'sine':
        this.waveform = Math.sin;
        break;

      case 'triangle':
        this.waveform = (x) => {
          if (x <= Math.PI) {
            return x / (Math.PI / 2) - 1;
          }
          return (x - (Math.PI)) / (-Math.PI / 2) + 1;
        };
        break;

      case 'square':
        this.waveform = (x) => {
          if (x <= Math.PI) {
            return -1;
          }
          return 1;
        };
        break;

      case 'sawtooth':
        this.waveform = x => x / Math.PI - 1;
        break;

      case 'noise':
        this.waveform = () => Math.random() * 2 - 1;
        break;

      default:
        this.waveform = param.waveform || this.waveform;
    }
  }

  reset() {
    this.startTime = new Date().getTime();
  }

  get value() {
    // const T = 1 / this.freq;
    const d = new Date().getTime();
    const a = (d - this.startTime) / 1000;
    let x = this.freq * a;
    x -= Math.floor(x);

    return (this.amplitude / 2) * this.waveform(x * (2 * Math.PI));
  }
}


export default LFO;