var instance = new GC.Spread.Sheets.Workbook(host,
                                            options,
                                            options.sheetCount,
                                            options.font,
                                            options.allowUserDragMerge,
                                            options.allowUserDragDrop,
                                            options.allowUserDragFill,
                                            options.allowUserZoom,
                                            options.allowUserResize,
                                            options.allowUndo,
                                            options.allowSheetReorder,
                                            options.allowContextMenu,
                                            options.allowUserDeselect,
                                            options.defaultDragFillType,
                                            options.showDragFillSmartTag,
                                            options.showHorizontalScrollbar,
                                            options.showVerticalScrollbar,
                                            options.scrollbarShowMax,
                                            options.scrollbarMaxAlign,
                                            options.tabStripVisible,
                                            options.tabStripRatio,
                                            options.tabEditable,
                                            options.newTabVisible,
                                            options.tabNavigationVisible,
                                            options.cutCopyIndicatorVisible,
                                            options.cutCopyIndicatorBorderColor,
                                            options.backColor,
                                            options.backgroundImage,
                                            options.backgroundImageLayout,
                                            options.grayAreaBackColor,
                                            options.showResizeTip,
                                            options.showDragDropTip,
                                            options.showDragFillTip,
                                            options.showScrollTip,
                                            options.scrollIgnoreHidden,
                                            options.highlightInvalidData,
                                            options.useTouchLayout,
                                            options.hideSelection,
                                            options.resizeZeroIndicator,
                                            options.allowUserEditFormula,
                                            options.enableFormulaTextbox,
                                            options.autoFitType,
                                            options.referenceStyle,
                                            options.calcOnDemand,
                                            options.allowCopyPasteExcelStyle,
                                            options.allowExtendPasteRange,
                                            options.copyPasteHeaderOptions,
                                            options.scrollByPixel,
                                            options.scrollPixel,
                                            options.customList);
var value; // Type: number
value = instance.getActiveSheetIndex();