simdjson-cppjs

simdjson compiled to WebAssembly via cpp.js, shipped as a workspace package, and demonstrated in a Vue 3 + Vite app.

Live benchmark

A browser benchmark that compares simdjson-wasm against the built-in JSON.parse on JSON of varying sizes, all running in your browser.

The benchmark page (live at the configured custom domain in packages/simdjson-example-vue/public/CNAME) does the following:

1. Generates JSON client-side from a seeded PRNG (deterministic across runs).
2. Runs each parser through warmup + measured iterations.
3. Reports median, p95, throughput (MB/s), and speedup vs the JSON.parse baseline.
4. Discloses the methodology (worker-boundary copies, std::string overhead, etc.) so the numbers are honest.

Parsers compared:

• JSON.parse on the main thread (baseline)
• JSON.parse in a Web Worker (apples-to-apples cross-thread cost)
• simdjson::dom running in WASM (full DOM tape — closest to JSON.parse semantics)
• simdjson::ondemand running in WASM (lazy iteration — typically the fastest)

Repository layout

packages/
  simdjson-wasm/          # C++ → WASM build (via cpp.js + simdjson v4.3.1)
  simdjson-example-vue/   # Vue 3 + Vite demo + benchmark page

Local development

pnpm install
pnpm --filter simdjson-vue-example dev
# open http://localhost:5173/         → benchmark
# open http://localhost:5173/#/demo   → file-upload demo

Production build

pnpm --filter simdjson-vue-example build
pnpm --filter simdjson-vue-example preview

Deploying to GitHub Pages with a custom domain

1. Push this repo to GitHub.
2. Enable Pages in repo settings → set the source to GitHub Actions.
3. Edit packages/simdjson-example-vue/public/CNAME to your domain (the file currently contains a placeholder).
4. Configure DNS:
   • Apex domain (example.com): A records to GitHub Pages IPs (185.199.108.153, .109.153, .110.153, .111.153) plus AAAA records (2606:50c0:8000::153 etc.).
   • Subdomain (bench.example.com): CNAME pointing to <user>.github.io.
5. Push to main. The workflow at .github/workflows/deploy.yml builds and deploys.
6. Wait 5-60 minutes for HTTPS to provision.

The workflow runs pnpm --filter simdjson-vue-example build and uploads the resulting dist/ to Pages.

Note: The large_test_data.json (1 GB) generated by packages/simdjson-example-vue/generate_json.mjs is .gitignored on purpose — it exceeds GitHub's 100 MB per-file limit. The benchmark page generates its own JSON in the browser; the local-file demo expects you to generate the file locally if you want to test it.