API Reference

API Reference

Initialization

initWasm()

Initialize the WASM module. Must be called once before any other operation.

import { initWasm } from 'modern-xlsx';
await initWasm();

I/O Functions

readFile(path: string): Promise<Workbook>

Read an XLSX file from disk. Node.js / Bun / Deno only.

readBuffer(data: Uint8Array): Promise<Workbook>

Read an XLSX file from a buffer. Works in all environments.

writeBlob(wb: Workbook): Blob

Write a workbook to a Blob for browser downloads.

Workbook

Constructor

const wb = new Workbook();

Properties

Property	Type	Description
sheetNames	string[]	Names of all sheets
sheetCount	number	Number of sheets
dateSystem	'date1900' | 'date1904'	Date epoch system
styles	StylesData	Styles collection
namedRanges	DefinedNameData[]	Named ranges
docProperties	DocPropertiesData | null	Document metadata
workbookViews	WorkbookViewData[]	View settings

Methods

Method	Returns	Description
addSheet(name)	Worksheet	Add a new sheet
getSheet(name)	Worksheet | undefined	Get sheet by name
getSheetByIndex(i)	Worksheet | undefined	Get sheet by index
removeSheet(nameOrIndex)	boolean	Remove a sheet
createStyle()	StyleBuilder	Create a style builder
addNamedRange(name, value, sheetId?)	void	Add named range
getNamedRange(name)	DefinedNameData | undefined	Get named range
removeNamedRange(name)	boolean	Remove named range
toBuffer()	Promise<Uint8Array>	Serialize to buffer
toFile(path)	Promise<void>	Write to file
toJSON()	WorkbookData	Get raw data

Worksheet

Properties

Property	Type	Description
name	string	Sheet name (read/write)
rows	RowData[]	All rows
columns	ColumnInfo[]	Column definitions
mergeCells	string[]	Merge ranges
autoFilter	AutoFilterData | null	Auto filter config
frozenPane	FrozenPane | null	Frozen pane config
hyperlinks	HyperlinkData[]	Hyperlinks
validations	DataValidationData[]	Validations
comments	CommentData[]	Cell comments
pageSetup	PageSetupData | null	Page setup
pageMargins	PageMarginsData | null	Page margins
sheetProtection	SheetProtectionData | null	Protection

Methods

Method	Returns	Description
cell(ref)	Cell	Get or create a cell
setColumnWidth(col, width)	void	Set column width
setRowHeight(row, height)	void	Set row height
setRowHidden(row, hidden)	void	Hide/show row
addMergeCell(range)	void	Add merge
removeMergeCell(range)	boolean	Remove merge
addHyperlink(ref, location, opts?)	void	Add link
removeHyperlink(ref)	boolean	Remove link
addValidation(ref, rule)	void	Add validation
removeValidation(ref)	boolean	Remove validation
addComment(ref, author, text)	void	Add comment
removeComment(ref)	boolean	Remove comment

Cell

Properties

Property	Type	Description
reference	string	Cell reference (e.g. "A1")
type	CellType	Value type
value	string | number | boolean | null	Cell value (read/write)
formula	string | null	Formula (read/write)
styleIndex	number | null	Style index (read/write)

StyleBuilder

Fluent builder for creating cell styles:

const idx = wb.createStyle()
  .font({ name: 'Arial', size: 12, bold: true, color: 'FF0000' })
  .fill({ pattern: 'solid', fgColor: 'FFFF00' })
  .border({ top: { style: 'thin', color: '000000' } })
  .alignment({ horizontal: 'center', wrapText: true })
  .protection({ locked: true })
  .numberFormat('#,##0.00')
  .build(wb.styles);

Utility Functions

Sheet Conversions

Function	Description
aoaToSheet(data, opts?)	Array-of-arrays to Worksheet
jsonToSheet(data, opts?)	JSON array to Worksheet
sheetToJson(ws, opts?)	Worksheet to JSON array
sheetToCsv(ws, opts?)	Worksheet to CSV string
sheetToHtml(ws, opts?)	Worksheet to HTML table
sheetAddAoa(ws, data, opts?)	Append array data
sheetAddJson(ws, data, opts?)	Append JSON data

Date Utilities

Function	Description
dateToSerial(date)	Date/Temporal to Excel serial
serialToDate(serial)	Excel serial to Date
isDateFormatId(id)	Check if built-in date format
isDateFormatCode(code)	Check if date format string

Cell References

Function	Description
encodeCellRef(row, col)	(0, 0) → "A1"
decodeCellRef(ref)	"A1" → { row: 0, col: 0 }
encodeRange(start, end)	Addresses to range string
decodeRange(range)	Range string to addresses
columnToLetter(col)	0 → "A"
letterToColumn(letter)	"A" → 0

Formatting

Function	Description
formatCell(value, format)	Format value with Excel format code
getBuiltinFormat(id)	Get built-in format string by ID