Node / SSR Usage

In Node servers (including SSR) you don't need browser assets and there is no initialization boilerplate: the engine locates the shipped modern-xlsx.wasm on disk (in this package's own dist/, pnpm-symlink-safe) and initializes it synchronously on first use. The explicit initWasmSync bootstrap from earlier versions is no longer required — keep it only if you want the one-off read+compile at startup instead of the first request.

Auto-initialization does a one-off synchronous file read plus WASM compile (measured ~20ms on this repo's dev machine, Node 22: ~4ms to read the 1.9MB binary, ~15ms to compile), charged to the first export. To move that cost to process startup instead, use the explicit init below.

Environment differences

Dimension	Browser	Node / SSR
Worker path	available	no Web Worker; falls back to main/stream
Auto download	triggers download	triggerDownload is a no-op
download option	defaults to true	already a no-op in Node; set false for explicitness and handle the Blob
Large data	worker + Fast stream	main → stream at ≥ 50k rows (main thread)
WASM init	auto-located (default)	auto-located and initialized

Export and write to disk

import { exportExcel } from "@marcusok/excel-exporter";
import { writeFile } from "node:fs/promises";

const result = await exportExcel({
  filename: "server-report",
  download: false, // never trigger a browser download server-side
  sheets: [{ name: "Sheet1", columns: [...], data: [...] }],
});

if (result.success && result.blob) {
  const buffer = Buffer.from(await result.blob.arrayBuffer());
  await writeFile("./server-report.xlsx", buffer);
}

With a framework (Next.js Route Handler)

// app/api/export/route.ts
import { exportExcel } from "@marcusok/excel-exporter";

export async function GET() {
  const result = await exportExcel({
    filename: "report",
    download: false,
    sheets: [/* ... */],
  });
  if (!result.success || !result.blob) {
    return Response.json({ error: result.error?.message }, { status: 500 });
  }
  return new Response(result.blob, {
    headers: {
      "Content-Type":
        "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet",
      "Content-Disposition": 'attachment; filename="report.xlsx"',
    },
  });
}

Optional: explicit init timing

To move the one-off synchronous WASM read+compile from the first request to process startup, await the loader before serving traffic:

import { getWasmLoader } from "@marcusok/excel-exporter";

await getWasmLoader().ensureLoaded(); // reads + compiles the shipped wasm once

Do not use initWasmSync from a separately installed modern-xlsx for this: the engine is bundled into this package's own dist, so an external copy initializes a different module instance and does not pre-warm the bundled one.

Bundler caveat: if your server build bundles this package and the WASM asset is not emitted alongside the bundle, the automatic disk lookup fails and WASM-dependent routes degrade to the style-less stream (headers/merges preserved). Either keep the package external (the default for Node server builds), pass configureWasm({ wasmUrl }) with an HTTP URL, or copy the asset where the bundle can read it.

Performance tip

Large server-side exports (≥ 50k rows) automatically take the stream path; without a Worker, Fast stream occupies the current thread for ~0.8s. Run it in an async task or queue so request threads stay responsive.