How to use WebAssembly (wasm) with create-react-app

Question

I use create-react-app and library with wasm its called sax-wasm. Slightly modifying the sample code for the web I got this:

import { SaxEventType, SAXParser } from 'sax-wasm';

async function loadAndPrepareWasm() {
  const saxWasmResponse = await import('sax-wasm/lib/sax-wasm.wasm');
  const saxWasmbuffer = await saxWasmResponse.arrayBuffer();
  const parser = new SAXParser(SaxEventType.Attribute | SaxEventType.OpenTag, {
    highWaterMark: 64 * 1024,
  });

  const ready = await parser.prepareWasm(new Uint8Array(saxWasmbuffer));
  if (ready) {
    return parser;
  }
}

loadAndPrepareWasm().then(console.log);

When I running yarn start command my build is failed:

Failed to compile.

./node_modules/sax-wasm/lib/sax-wasm.wasm
Module parse failed: magic header not detected
File was processed with these loaders:
 * ./node_modules/file-loader/dist/cjs.js
You may need an additional loader to handle the result of these loaders.
Error: magic header not detected

Answer 1

The following solution is for CRA 3.x. For CRA 4.x you should use craco.

CRA does not support WASM. But you can workaround it. You need to override webpack config. There are multiple packages that can do it. I used react-app-rewired. And you need the wasm-loader package

Than add your override config-overrides.js:

const path = require('path');

module.exports = function override(config, env) {

    /**
     * Add WASM support
     */

    // Make file-loader ignore WASM files
    const wasmExtensionRegExp = /\.wasm$/;
    config.resolve.extensions.push('.wasm');
    config.module.rules.forEach(rule => {
        (rule.oneOf || []).forEach(oneOf => {
            if (oneOf.loader && oneOf.loader.indexOf('file-loader') >= 0) {
                oneOf.exclude.push(wasmExtensionRegExp);
            }
        });
    });

    // Add a dedicated loader for WASM
    config.module.rules.push({
        test: wasmExtensionRegExp,
        include: path.resolve(__dirname, 'src'),
        use: [{ loader: require.resolve('wasm-loader'), options: {} }]
    });

    return config;
};

In package.json I did it like this:

{
...
  "scripts": {
    "start": "react-app-rewired start",
    "build": "react-app-rewired build",
    "test": "react-app-rewired test",
    "eject": "react-scripts eject",
    "predeploy": "npm run build",
    "deploy": "gh-pages -d build"
  },
...
  "devDependencies": {
    "react-app-rewired": "2.1.3",
    "wasm-loader": "1.3.0"
  }
}