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Parsing Options, read_opts) attempts to parse data.

XLSX.readFile(filename, read_opts) attempts to read filename and parse.

The read functions accept an options argument:

Option NameDefaultDescription
typeInput data encoding (see Input Type below)
rawfalseIf true, plain text parsing will not parse values **
densefalseIf true, use a dense worksheet representation **
codepageIf specified, use code page when appropriate **
cellFormulatrueSave formulae to the .f field
cellHTMLtrueParse rich text and save HTML to the .h field
cellNFfalseSave number format string to the .z field
cellStylesfalseSave style/theme info to the .s field
cellTexttrueGenerated formatted text to the .w field
cellDatesfalseStore dates as type d (default is n)
dateNFIf specified, use the string for date code 14 **
sheetStubsfalseCreate cell objects of type z for stub cells
sheetRows0If >0, read the first sheetRows rows **
bookDepsfalseIf true, parse calculation chains
bookFilesfalseIf true, add raw files to book object **
bookPropsfalseIf true, only parse enough to get book metadata **
bookSheetsfalseIf true, only parse enough to get the sheet names
bookVBAfalseIf true, copy VBA blob to vbaraw field **
password""If defined and file is encrypted, use password **
WTFfalseIf true, throw errors on unexpected file features **
sheetsIf specified, only parse specified sheets **
PRNfalseIf true, allow parsing of PRN files **
xlfnfalseIf true, preserve _xlfn. prefixes in formulae **
FSDSV Field Separator override
  • Even if cellNF is false, formatted text will be generated and saved to .w
  • In some cases, sheets may be parsed even if bookSheets is false.
  • Excel aggressively tries to interpret values from CSV and other plain text. This leads to surprising behavior! The raw option suppresses value parsing.
  • bookSheets and bookProps combine to give both sets of information
  • Deps will be an empty object if bookDeps is false
  • bookFiles behavior depends on file type:
    • keys array (paths in the ZIP) for ZIP-based formats
    • files hash (mapping paths to objects representing the files) for ZIP
    • cfb object for formats using CFB containers
  • sheetRows-1 rows will be generated when looking at the JSON object output (since the header row is counted as a row when parsing the data)
  • By default all worksheets are parsed. sheets restricts based on input type:
    • number: zero-based index of worksheet to parse (0 is first worksheet)
    • string: name of worksheet to parse (case insensitive)
    • array of numbers and strings to select multiple worksheets.
  • bookVBA merely exposes the raw VBA CFB object. It does not parse the data. XLSM and XLSB store the VBA CFB object in xl/vbaProject.bin. BIFF8 XLS mixes the VBA entries alongside the core Workbook entry, so the library generates a new blob from the XLS CFB container that works in XLSM and XLSB files.
  • codepage is applied to BIFF2 - BIFF5 files without CodePage records and to CSV files without BOM in type:"binary". BIFF8 XLS always defaults to 1200.
  • PRN affects parsing of text files without a common delimiter character.
  • Currently only XOR encryption is supported. Unsupported error will be thrown for files employing other encryption methods.
  • Newer Excel functions are serialized with the _xlfn. prefix, hidden from the user. SheetJS will strip _xlfn. normally. The xlfn option preserves them.
  • WTF is mainly for development. By default, the parser will suppress read errors on single worksheets, allowing you to read from the worksheets that do parse properly. Setting WTF:true forces those errors to be thrown.
  • By default, "sparse" mode worksheets are generated. Individual cells are accessed by indexing the worksheet object with an A1-Style address. "dense" worksheets store cells in an array of arrays at sheet["!data"].

Input Type

Strings can be interpreted in multiple ways. The type parameter for read tells the library how to parse the data argument:

typeexpected input
"base64"string: Base64 encoding of the file
"binary"string: binary string (byte n is data.charCodeAt(n))
"string"string: JS string (only appropriate for UTF-8 text formats)
"buffer"nodejs Buffer
"array"array: array of 8-bit unsigned int (byte n is data[n])
"file"string: path of file that will be read (nodejs only)

Some common types are automatically deduced from the data input type, including NodeJS Buffer objects, Uint8Array and ArrayBuffer objects, and arrays of numbers.

When a JS string is passed with no type, the library assumes the data is a Base64 string. FileReader#readAsBinaryString or ASCII data requires "binary" type. DOM strings including FileReader#readAsText should use type "string".

Guessing File Type

Implementation Details (click to show)

Excel and other spreadsheet tools read the first few bytes and apply other heuristics to determine a file type. This enables file type punning: renaming files with the .xls extension will tell your computer to use Excel to open the file but Excel will know how to handle it. This library applies similar logic:

Byte 0Raw File TypeSpreadsheet Types
0xD0CFB ContainerBIFF 5/8 or protected XLSX/XLSB or WQ3/QPW or XLR
0x09BIFF StreamBIFF 2/3/4/5
0x3CXML/HTMLSpreadsheetML / Flat ODS / UOS1 / HTML / plain text
0x50ZIP ArchiveXLSB or XLSX/M or ODS or UOS2 or NUMBERS or text
0x49Plain TextSYLK or plain text
0x54Plain TextDIF or plain text
0xEFUTF-8 TextSpreadsheetML / Flat ODS / UOS1 / HTML / plain text
0xFFUTF-16 TextSpreadsheetML / Flat ODS / UOS1 / HTML / plain text
0x00Record StreamLotus WK* or Quattro Pro or plain text
0x7BPlain textRTF or plain text
0x0APlain textSpreadsheetML / Flat ODS / UOS1 / HTML / plain text
0x0DPlain textSpreadsheetML / Flat ODS / UOS1 / HTML / plain text
0x20Plain textSpreadsheetML / Flat ODS / UOS1 / HTML / plain text

DBF files are detected based on the first byte as well as the third and fourth bytes (corresponding to month and day of the file date)

Works for Windows files are detected based on the BOF record with type 0xFF

Plain text format guessing follows the priority order:

XML<?xml appears in the first 1024 characters
HTMLstarts with < and HTML tags appear in the first 1024 characters *
XMLstarts with < and the first tag is valid
RTFstarts with {\rt
DSVstarts with /sep=.$/, separator is the specified character
DSVmore unquoted `
DSVmore unquoted ; chars than \t or , in the first 1024
TSVmore unquoted \t chars than , chars in the first 1024
CSVone of the first 1024 characters is a comma ","
ETHstarts with socialcalc:version:
PRNPRN option is set to true
  • HTML tags include: html, table, head, meta, script, style, div
Why are random text files valid? (click to show)

Excel is extremely aggressive in reading files. Adding an XLS extension to any display text file (where the only characters are ANSI display chars) tricks Excel into thinking that the file is potentially a CSV or TSV file, even if it is only one column! This library attempts to replicate that behavior.

The best approach is to validate the desired worksheet and ensure it has the expected number of rows or columns. Extracting the range is extremely simple:

var range = XLSX.utils.decode_range(worksheet['!ref']);
var ncols = range.e.c - range.s.c + 1, nrows = range.e.r - range.s.r + 1;