Writing files

Use write to get the file content in memory. Use writeFile to save it in Node. writeFile takes the format from the file extension. Both serialize synchronously. writeFileSync is an alias of writeFile. writeFileAsync serializes synchronously and then saves the file asynchronously through Node’s file system; it does not move the engine work off the calling thread.

const XLSX = require("@agent-sheet/wasm");

const wb = XLSX.read("a,b\n1,2\n3,4", { type: "string" });
XLSX.writeFile(wb, "out.xlsx");          // format from the extension
XLSX.writeFile(wb, "out.csv");
console.log(XLSX.readFile("out.xlsx").Sheets.Sheet1["!ref"]);
console.log(JSON.stringify(XLSX.write(wb, { type: "string", bookType: "csv" })));

Output

A1:B3
"a,b\n1,2\n3,4"

In a browser, writeFile starts a download. See Browsers and CSP.

Output types

type	write returns
"string"	text (text formats only)
"base64"	base64 text
"binary"	a binary string
"buffer"	a Node Buffer
"array"	an ArrayBuffer

const XLSX = require("@agent-sheet/wasm");
const wb = XLSX.utils.book_new();
XLSX.utils.book_append_sheet(wb, XLSX.utils.aoa_to_sheet([["a", 1]]), "S");

console.log(typeof XLSX.write(wb, { type: "base64" }));
console.log(typeof XLSX.write(wb, { type: "binary" }));
console.log(XLSX.write(wb, { type: "array" }).constructor.name);
console.log(Buffer.isBuffer(XLSX.write(wb, { type: "buffer" })));

Output

string
string
ArrayBuffer
true

Choose the format

Set bookType. The default is "xlsx". See Supported formats for every value.

const XLSX = require("@agent-sheet/wasm");
const wb = XLSX.utils.book_new();
XLSX.utils.book_append_sheet(wb, XLSX.utils.aoa_to_sheet([["a", "b"], [1, 2]]), "First");
XLSX.utils.book_append_sheet(wb, XLSX.utils.aoa_to_sheet([["x"], [9]]), "Second");

console.log(XLSX.write(wb, { type: "string", bookType: "csv" }));
console.log(JSON.stringify(XLSX.write(wb, { type: "string", bookType: "csv", sheet: "Second" })));
console.log(XLSX.write(wb, { type: "string", bookType: "csv", FS: ";", RS: "|" }));

Output

a,b
1,2
"x\n9"
a;b|1;2

Single-sheet formats such as CSV write the first sheet. Use the sheet option (a name or an index) to write another one.

Compression

ZIP-based formats (XLSX, XLSM, XLSB, ODS) are stored without compression by default. Set compression: true to deflate the entries:

const XLSX = require("@agent-sheet/wasm");
const rows = Array.from({ length: 200 }, (_, i) => ["row", i, "same text again and again"]);
const wb = XLSX.utils.book_new();
XLSX.utils.book_append_sheet(wb, XLSX.utils.aoa_to_sheet(rows), "S");

const plain = XLSX.write(wb, { type: "buffer", bookType: "xlsx" });
const small = XLSX.write(wb, { type: "buffer", bookType: "xlsx", compression: true });
console.log(small.length < plain.length);

Output

true

Document properties

wb.Props holds the standard properties and wb.Custprops holds custom ones. Both are written with the workbook.

const XLSX = require("@agent-sheet/wasm");
const wb = XLSX.utils.book_new();
XLSX.utils.book_append_sheet(wb, XLSX.utils.aoa_to_sheet([[1]]), "S");
wb.Props = { Title: "Report", Author: "Ann" };
wb.Custprops = { Project: "x" };

const back = XLSX.read(XLSX.write(wb, { type: "buffer", bookType: "xlsx" }));
console.log(back.Props.Title, back.Props.Author, back.Custprops);

Output

Report Ann { Project: 'x' }

Main write options

See Writing options for the full list.

Option	Effect
type	output representation
bookType	output format
cellStyles	export styles and presentation data
bookSST	write a shared string table
compression	deflate ZIP entries
sheet	sheet for single-sheet formats
FS, RS	separators for text output
Props	document properties to write instead of wb.Props