code: function vectorLengthsAreEqual (x, y, eps) {
    return isZero(x.length() - y.length(), eps);
  }
docs: Test if a vector length is equal to another vector length within a tolerance.
  @function vectorLengthsAreEqual
  @memberof Compare
  @param {Vector2|Vector3|Vector4} x The first vector.
  @param {Vector2|Vector3|Vector4} y The second vector.
  @param {number} eps The numerical tolerance.
  @returns {boolean} True if vector length difference is within the numerical tolerance, false if not.