code: function blank(v) {
      if (typeof v === 'undefined') return true;
      if (v instanceof Array && v.length === 0) return true;
      if (v === null) return true;
      if (typeof v === 'string' && v === '') return true;
      return false;
  }
docs: Return true when v is undefined, blank array, null or empty string
  otherwise returns false
  
  @param {Mix} v
  @returns {Boolean} whether `v` blank or not