code: function calcBlocks() {
      return {
        total: Math.ceil(this.props.total / this.props.visiblePages),
        current: Math.ceil(this.props.current / this.props.visiblePages),
        size: this.props.visiblePages
      };
    }
docs: /* ========================= HELPERS ============================== 
  Calculates "blocks" of buttons with page numbers.