code: function Quat2Angle(x, y, z, w) {
    const test = x * y + z * w;
  
    // singularity at north pole
    if (test > 0.499) {
      const yaw = 2 * Math.atan2(x, w);
      const pitch = Math.PI / 2;
      const roll = 0;
  
      return new THREE.Vector3(pitch, roll, yaw);
    }
  
    // singularity at south pole
    if (test < -0.499) {
      const yaw = -2 * Math.atan2(x, w);
      const pitch = -Math.PI / 2;
      const roll = 0;
  
      return new THREE.Vector3(pitch, roll, yaw);
    }
  
    const sqx = x * x;
    const sqy = y * y;
    const sqz = z * z;
    const yaw = Math.atan2(2 * y * w - 2 * x * z, 1 - 2 * sqy - 2 * sqz);
    const pitch = Math.asin(2 * test);
    const roll = Math.atan2(2 * x * w - 2 * y * z, 1 - 2 * sqx - 2 * sqz);
  
    return new THREE.Vector3(pitch, roll, yaw);
  }
docs: Convert a quaternion to an angle
  
  Taken from https://stackoverflow.com/a/35448946
  Thanks P. Ellul