if (typeof DelayNode !== 'undefined') {

  class FeedbackDelayNode extends DelayNode {

    constructor(ac, wet, time, feedback) {

      super(ac);

      wet = Math.abs(wet);

      this.delayTime.value = time;

      const feedbackGain = ac.createGain();

      feedbackGain.gain.value = Math.min(Math.abs(feedback), 0.995);

      this.feedback = feedbackGain.gain;

      const delayGain = ac.createGain();

      delayGain.gain.value = wet;

      this.delayGain = delayGain;

      this.connect(feedbackGain);

      this.connect(delayGain);

      feedbackGain.connect(this);

      this.connect = (target) => delayGain.connect(target);

      return this;

    }

    start(t) {

      this.delayGain.gain.setValueAtTime(this.delayGain.gain.value, t + this.delayTime.value);

    }

  }

  AudioContext.prototype.createFeedbackDelay = function (wet, time, feedback) {

    return new FeedbackDelayNode(this, wet, time, feedback);

  };

}