code: function setVersion(type, ver) {
  
    const idx = verMap[type];
    let cur = verArr[idx];
    let next = cur + 1;
  
    if (isTruthy(ver))
      next = ver;
  
    if (isTruthy(ver)) {
      verArr[idx] = ver;
    }
  
    else {
      if (type === 'patch') {
        if (next > maxPatch) {
          // zero current stepping
          // up to minor.
          verArr[idx] = 0;
          return setVersion('minor');
        }
        else {
          verArr[idx] = next;
        }
      }
      else if (type === 'minor') {
        if (next > maxMinor) {
          // zero current stepping
          // up to major.
          verArr[idx] = 0;
          return setVersion('major');
        }
        else {
          verArr[idx] = next;
        }
      }
      else {
        verArr[idx] = next;
      }
    }
  
  }
docs: Recursive for setting version.