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Data Export

Writing Workbooks


Generate spreadsheet bytes (file) from data

var data = XLSX.write(workbook, opts);

The write method attempts to package data from the workbook into a file in memory. By default, XLSX files are generated, but that can be controlled with the bookType property of the opts argument. Based on the type option, the data can be stored as a "binary string", JS string, Uint8Array or Buffer.

The second opts argument is required. "Writing Options" covers the supported properties and behaviors.

Generate and attempt to save file

XLSX.writeFile(workbook, filename, opts);

The writeFile method packages the data and attempts to save the new file. The export file format is determined by the extension of filename (SheetJS.xlsx signals XLSX export, SheetJS.xlsb signals XLSB export, etc).

The second opts argument is optional. "Writing Options" covers the supported properties and behaviors.

Generate and attempt to save an XLSX file

XLSX.writeFileXLSX(workbook, filename, opts);

The writeFile method embeds a number of different export functions. This is great for developer experience but not amenable to tree shaking using the current developer tools. When only XLSX exports are needed, this method avoids referencing the other export functions.

The second opts argument is optional. "Writing Options" covers the supported properties and behaviors.


The writeFile and writeFileXLSX methods uses platform-specific APIs to save files. The APIs do not generally provide feedback on whether files were created.


Here are a few common scenarios (click on each subtitle to see the code).

The demos cover special deployments in more detail.

Example: Local File

XLSX.writeFile supports writing local files in platforms like NodeJS. In other platforms like React Native, XLSX.write should be called with file data.

XLSX.writeFile wraps a few techniques for triggering a file save:

  • URL browser API creates an object URL for the file, which the library uses by creating a link and forcing a click. It is supported in modern browsers.
  • msSaveBlob is an IE10+ API for triggering a file save.
  • IE_FileSave uses VBScript and ActiveX to write a file in IE6+ for Windows XP and Windows 7. The shim must be included in the containing HTML page.

There is no standard way to determine if the actual file has been downloaded.

/* output format determined by filename */
XLSX.writeFile(workbook, "out.xlsb");
/* at this point, out.xlsb will have been downloaded */
SWF workaround for Windows 95+ (click to show)

Each moving part in this solution has been deprecated years ago:

  • Adobe stopped supporting Flash Player at the end of 2020
  • Microsoft stopped supporting IE8 in 2019 and stopped supporting IE9 in 2020
  • Downloadify support ended in 2010 and SWFObject support ended in 2016

New projects should strongly consider requiring modern browsers. This info is provided on an "as is" basis and there is no realistic way to provide support given that every related vendor stopped providing support for their software.

XLSX.writeFile techniques work for most modern browsers as well as older IE. For much older browsers, there are workarounds implemented by wrapper libraries.

Downloadify uses a Flash SWF button to generate local files, suitable for environments where ActiveX is unavailable:

/* other options are required! read the downloadify docs for more info */
filename: "test.xlsx",
data: function() { return XLSX.write(wb, {bookType:"xlsx", type:"base64"}); },
append: false,
dataType: "base64"

The oldie demo shows an IE-compatible fallback scenario.

Example: Remote File

This example focuses on uploading files ("Ajax" in browser parlance) using APIs like XMLHttpRequest and fetch as well as third-party libraries.


Some platforms like Azure and AWS will attempt to parse POST request bodies as UTF-8 strings before user code can see the data. This will result in corrupt data parsed by the server. There are some workarounds, but the safest approach is to adjust the server process or Lambda function to accept Base64 strings.

A complete example using XHR is included in the XHR demo, along with examples for fetch and wrapper libraries. This example assumes the server can handle Base64-encoded files (see the demo for a basic nodejs server):

/* in this example, send a base64 string to the server */
var wbout = XLSX.write(workbook, { bookType: "xlsx", type: "base64" });

/* prepare data for POST */
var formdata = new FormData();
formdata.append("file", "test.xlsx"); // <-- server expects `file` to hold name
formdata.append("data", wbout); // <-- `data` holds the base64-encoded data

/* perform POST request */
var req = new XMLHttpRequest();"POST", "/upload", true);

For servers that do not parse POST request bodies as UTF-8 strings, a Blob can be generated from the array output:

/* in this example, send a Blob to the server */
var wbout = XLSX.write(workbook, { bookType: "xlsx", type: "array" });

/* prepare data for POST */
var blob = new Blob([new Uint8Array(wbout)], {type:"application/octet-stream"});
var formdata = new FormData();
formdata.append("file", blob, "test.xlsx");

/* perform POST request */
fetch("/upload", { method: 'POST', body: formdata });

Generating JSON and JS Data

JSON and JS data tend to represent single worksheets. The utility functions in this section work with single worksheets.

The "Common Spreadsheet Format" section describes the object structure in more detail. workbook.SheetNames is an ordered list of the worksheet names. workbook.Sheets is an object whose keys are sheet names and whose values are worksheet objects.

The "first worksheet" is stored at workbook.Sheets[workbook.SheetNames[0]].


Create an array of JS objects from a worksheet

var jsa = XLSX.utils.sheet_to_json(worksheet, opts);

Create an array of arrays of JS values from a worksheet

var aoa = XLSX.utils.sheet_to_json(worksheet, {...opts, header: 1});

The sheet_to_json utility function walks a workbook in row-major order, generating an array of objects. The second opts argument controls a number of export decisions including the type of values (JS values or formatted text). The "JSON" section describes the argument in more detail.

By default, sheet_to_json scans the first row and uses the values as headers. With the header: 1 option, the function exports an array of arrays of values.


Example: Data Grids

x-spreadsheet is an interactive data grid for previewing and modifying structured data in the web browser. The demo includes a sample script with the stox function for converting from a workbook to x-spreadsheet. Live Demo:

Example: Data Loading

Populating a database (SQL or no-SQL) (click to show)

The database demo includes examples of working with databases and query results.

Numerical Computations with TensorFlow.js (click to show)

@tensorflow/tfjs and other libraries expect data in simple arrays, well-suited for worksheets where each column is a data vector. That is the transpose of how most people use spreadsheets, where each row is a vector.

A single Array#map can pull individual named rows from sheet_to_json export:

const XLSX = require("xlsx");
const tf = require('@tensorflow/tfjs');

const key = "age"; // this is the field we want to pull
const ages = XLSX.utils.sheet_to_json(worksheet).map(r => r[key]);
const tf_data = tf.tensor1d(ages);

All fields can be processed at once using a transpose of the 2D tensor generated with the sheet_to_json export with header: 1. The first row, if it contains header labels, should be removed with a slice:

const XLSX = require("xlsx");
const tf = require('@tensorflow/tfjs');

/* array of arrays of the data starting on the second row */
const aoa = XLSX.utils.sheet_to_json(worksheet, {header: 1}).slice(1);
/* dataset in the "correct orientation" */
const tf_dataset = tf.tensor2d(aoa).transpose();
/* pull out each dataset with a slice */
const tf_field0 = tf_dataset.slice([0,0], [1,tensor.shape[1]]).flatten();
const tf_field1 = tf_dataset.slice([1,0], [1,tensor.shape[1]]).flatten();

The array demo shows a complete example.

Generating HTML Tables


Generate HTML Table from Worksheet

var html = XLSX.utils.sheet_to_html(worksheet);

The sheet_to_html utility function generates HTML code based on the worksheet data. Each cell in the worksheet is mapped to a <TD> element. Merged cells in the worksheet are serialized by setting colspan and rowspan attributes.


The sheet_to_html utility function generates HTML code that can be added to any DOM element by setting the innerHTML:

var container = document.getElementById("tavolo");
container.innerHTML = XLSX.utils.sheet_to_html(worksheet);

Combining with fetch, constructing a site from a workbook is straightforward:

This example assigns the innerHTML of a DIV element:

<style>TABLE { border-collapse: collapse; } TD { border: 1px solid; }</style>
<div id="tavolo"></div>
<script src=""></script>
<script type="text/javascript">
(async() => {
/* fetch and parse workbook -- see the fetch example for details */
const workbook = (await fetch("sheetjs.xlsx")).arrayBuffer());

let output = [];
/* loop through the worksheet names in order */
workbook.SheetNames.forEach(name => {

/* generate HTML from the corresponding worksheets */
const worksheet = workbook.Sheets[name];
const html = XLSX.utils.sheet_to_html(worksheet);

/* add a header with the title name followed by the table */
/* write to the DOM at the end */
tavolo.innerHTML = output.join("\n");

Generating Single-Worksheet Snapshots

The sheet_to_* functions accept a worksheet object.


Generate a CSV from a single worksheet

var csv = XLSX.utils.sheet_to_csv(worksheet, opts);

This snapshot is designed to replicate the "CSV UTF8 (.csv)" output type. "Delimiter-Separated Output" describes the function and the optional opts argument in more detail.

Generate "Text" from a single worksheet

var txt = XLSX.utils.sheet_to_txt(worksheet, opts);

This snapshot is designed to replicate the "UTF16 Text (.txt)" output type. "Delimiter-Separated Output" describes the function and the optional opts argument in more detail.

Generate a list of formulae from a single worksheet

var fmla = XLSX.utils.sheet_to_formulae(worksheet);

This snapshot generates an array of entries representing the embedded formulae. Array formulae are rendered in the form range=formula while plain cells are rendered in the form cell=formula or value. String literals are prefixed with an apostrophe ', consistent with Excel's formula bar display.

"Formulae Output" describes the function in more detail.

Streaming Write

The streaming write functions are available in the object. They take the same arguments as the normal write functions but return a NodeJS Readable Stream.

  • is the streaming version of XLSX.utils.sheet_to_csv.
  • is the streaming version of XLSX.utils.sheet_to_html.
  • is the streaming version of XLSX.utils.sheet_to_json.
nodejs convert to CSV and write file (click to show)
var output_file_name = "out.csv";
var stream =;
nodejs write JSON stream to screen (click to show)
/* to_json returns an object-mode stream */
var stream =, {raw:true});

/* the following stream converts JS objects to text via JSON.stringify */
var conv = new Transform({writableObjectMode:true});
conv._transform = function(obj, e, cb){ cb(null, JSON.stringify(obj) + "\n"); };

stream.pipe(conv); conv.pipe(process.stdout); pipes write streams to nodejs response.