Node.js Preset

Convenience helpers for running JavaScript/Node.js code in machinees.

TypeScript: NodeMachine Class

The NodeMachine class provides Node.js-specific methods.

import { NodeMachine } from 'smolvm';

const machine = await NodeMachine.create({ name: 'node-env' });

try {
  // Run JavaScript code
  const result = await machine.runCode(`
    console.log("Node.js version:", process.version);
    console.log("Platform:", process.platform);
    console.log("Architecture:", process.arch);
  `);
  console.log(result.stdout);

  // Run ES modules
  const esmResult = await machine.runESM(`
    const add = (a, b) => a + b;
    console.log("2 + 3 =", add(2, 3));
  `);
  console.log(esmResult.stdout);

  // Check Node.js version
  const version = await machine.version();
  console.log(version);  // "22.x.x"

  // Install packages
  await machine.npm(['lodash', 'axios']);

  // Run with installed packages
  const withPackages = await machine.runCode(`
    const _ = require('lodash');
    console.log(_.chunk([1, 2, 3, 4, 5], 2));
  `);
} finally {
  await machine.stop();
  await machine.delete();
}

Methods

Method	Description
runCode(code)	Execute CommonJS code
runESM(code)	Execute ES module code
runFile(path)	Execute a JavaScript file
npm(packages)	Install packages with npm
version()	Get Node.js version

Python: Preset Function

from smolvm.presets import node_machine

# Execute JavaScript code
result = await node_machine("""
console.log("Node.js version:", process.version);

const data = { message: "Hello from Node.js!" };
console.log(JSON.stringify(data, null, 2));
""")
print(result.stdout)

CommonJS vs ES Modules

CommonJS (Default)

const result = await machine.runCode(`
const fs = require('fs');
const path = require('path');

console.log(path.join('/tmp', 'test.txt'));
`);

ES Modules

const result = await machine.runESM(`
import { readFileSync } from 'fs';
import { join } from 'path';

console.log(join('/tmp', 'test.txt'));
`);

Installing Packages

const machine = await NodeMachine.create({ name: 'with-packages' });

// Install packages
await machine.npm(['express', 'cors', 'helmet']);

// Use them
const result = await machine.runCode(`
const express = require('express');
const cors = require('cors');

// Just verify imports work
console.log('Express version:', require('express/package.json').version);
console.log('Packages loaded successfully!');
`);

TypeScript Execution

For TypeScript, use ts-node or compile first:

const machine = await NodeMachine.create({ name: 'typescript' });

// Install TypeScript tools
await machine.npm(['typescript', 'ts-node', '@types/node']);

// Run TypeScript with ts-node
const result = await machine.runCode(`
const { execSync } = require('child_process');
const code = \`
interface User {
  name: string;
  age: number;
}
const user: User = { name: "Alice", age: 30 };
console.log(user);
\`;

require('fs').writeFileSync('/tmp/test.ts', code);
console.log(execSync('npx ts-node /tmp/test.ts').toString());
`);

HTTP Server Example

const machine = await NodeMachine.create({
  name: 'http-server',
  ports: [{ host: 3000, guest: 3000 }]
});

await machine.npm(['express']);

// Start server in background
machine.exec(['node', '-e', `
const express = require('express');
const app = express();

app.get('/', (req, res) => {
  res.json({ message: 'Hello from machine!' });
});

app.listen(3000, () => {
  console.log('Server running on port 3000');
});
`]);

// Server is now accessible at localhost:3000

Working with Files

const machine = await NodeMachine.create({
  name: 'file-processor',
  mounts: [
    { source: '/data/input', target: '/input', readonly: true },
    { source: '/data/output', target: '/output' }
  ]
});

const result = await machine.runCode(`
const fs = require('fs');
const path = require('path');

// Read input files
const files = fs.readdirSync('/input');
console.log('Input files:', files);

// Process each file
for (const file of files) {
  const content = fs.readFileSync(path.join('/input', file), 'utf8');
  const processed = content.toUpperCase();
  fs.writeFileSync(path.join('/output', file), processed);
}

console.log('Processing complete!');
`);

JSON Processing

const machine = await NodeMachine.create({ name: 'json-processor' });

const result = await machine.runCode(`
const data = {
  users: [
    { id: 1, name: 'Alice' },
    { id: 2, name: 'Bob' }
  ]
};

// Transform data
const transformed = data.users.map(u => ({
  ...u,
  email: \`\${u.name.toLowerCase()}@example.com\`
}));

console.log(JSON.stringify(transformed, null, 2));
`);

const output = JSON.parse(result.stdout);
console.log(output);