lazy-sparql-result-reader

A fast SPARQL results parser for JavaScript and TypeScript, compiled from Rust via WebAssembly.
It reads streamed SPARQL query results and calls a callback for each parsed batch of bindings.

Features

• Processes streaming SPARQL results efficiently.
• Calls a JavaScript callback for each batch of parsed bindings.
• Written in Rust for speed and reliability.
• Fully compatible with TypeScript.

Usage Example

1. Install dependencies

npm install  lazy-sparql-result-reader vite @vitejs/plugin-wasm

2. Configure Vite for WASM

Create or update vite.config.ts:

import { defineConfig } from 'vite';
import wasm from '@vitejs/plugin-wasm';

export default defineConfig({
  plugins: [wasm()],
});

This allows Vite to correctly load WebAssembly modules.

3. Use the parser in your app

import init, { read } from "lazy-sparql-result-reader?init";

// Initialize the WASM module
await init();

fetch("https://qlever.dev/api/wikidata", {
  method: 'POST',
  headers: {
    "Accept": "application/sparql-results+json",
    "Content-Type": "application/x-www-form-urlencoded;charset=UTF-8",
  },
  body: new URLSearchParams({
    query: "SELECT * {?s ?p ?o} LIMIT 1000",
  })
})
.then(async response => {
  if (!response.ok) {
    throw new Error(`SPARQL request failed: ${response.status}`);
  }
  const stream = response.body; // ReadableStream of the SPARQL JSON results
  if (!stream) throw new Error("Response has no body stream");
  // Parse the streamed results with the WASM parser
  await read(stream, 100, (bindings) => {
    console.log("Received batch of bindings:", bindings);
  });
})
.catch((err) => {
  console.error("Error fetching or parsing SPARQL results:", err);
});

Notes

• The first callback invocation contains the SPARQL head, i.e., the variable names in the result set.
• Subsequent callback invocations contain batches of bindings as they are parsed.
• batch_size controls how many bindings are buffered before each callback.
• Ensure your environment supports ReadableStream (modern browsers or Node.js >= 18).

This setup allows your JS/TS application to process streaming SPARQL results efficiently,
with immediate access to the head and incremental batches of bindings.

License

This project is licensed under the MIT License.

You are free to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the software, under the conditions of the MIT License.

For full details, see the LICENSE file.