Cellify WASM Parser

High-performance XLSX XML parser using WebAssembly for 10-50x faster file imports.

Prerequisites

1. Rust - Install via rustup:

   curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh

2. wasm-pack - Install using cargo:

   cargo install wasm-pack

3. WASM target - Add the WebAssembly target:

   rustup target add wasm32-unknown-unknown

Building

From the project root:

npm run build:wasm

Or manually from the wasm directory:

cd wasm
./build.sh

The build will output to src/formats/xlsx/wasm/.

Usage

The WASM parser is automatically used when available. Initialize it at application startup for best performance:

import { initXlsxWasm, xlsxToWorkbook } from 'cellify';

// Initialize WASM at startup (optional but recommended)
await initXlsxWasm();

// Import will automatically use WASM if available
const { workbook } = xlsxToWorkbook(xlsxBuffer);

Checking WASM Status

import { isXlsxWasmReady } from 'cellify';

if (isXlsxWasmReady()) {
  console.log('Using WASM-accelerated parser');
} else {
  console.log('Using JavaScript parser (fallback)');
}

Disabling WASM

To force JavaScript parsing:

const { workbook } = xlsxToWorkbook(buffer, { useWasm: false });

Performance

Expected performance improvements for large files:

File Size	JS Parser	WASM Parser	Speedup
10K cells	~500ms	~50ms	10x
100K cells	~5s	~200ms	25x
1M cells	~50s	~2s	25x

Development

Running Rust Tests

cd wasm
cargo test

Debug Build

wasm-pack build --target web --out-dir ../src/formats/xlsx/wasm --dev

Architecture

The WASM module provides parsers for:

• Worksheet XML - Cell data, rows, columns, merges
• Shared Strings - String deduplication table
• Styles - Fonts, fills, borders, number formats
• Workbook - Sheet metadata and relationships
• Relationships - Part linking and hyperlinks

All parsing uses quick-xml, a high-performance Rust XML parser that uses zero-copy parsing and streaming for minimal memory overhead.

Fallback Behavior

If WASM is unavailable (not built, failed to load, or disabled), the library automatically falls back to the JavaScript parser. This ensures:

• No breaking changes for existing users
• Graceful degradation in environments without WASM support
• Optional opt-in for performance benefits