Quick overview: Node.js
Use the editor above to run a small Node.js idea without setting up a project first. The Node.js editor uses Monaco and sends code to Piston through the local app script, then returns stdout and stderr to the result panel. Run it. Read the output. Then change one thing, because the fastest debugging session is usually the one with the fewest moving parts.
We built this page for short checks: server-side JavaScript syntax, stdin parsing, async/await, JSON transforms, and shareable snippets. It is deliberately narrower than a local environment, and that is the point; when a snippet is only twenty lines long, a full toolchain can get in the way of the question you actually have.
Node is not the browser: window and the DOM are absent, while CommonJS and many runtime globals are normal. If you are checking a stream, a regex, or an async snippet, this page earns its keep.
What happens when Run fires
The loop is intentionally plain. Write code in the main editor, provide STDIN or arguments if the page exposes those controls, and press Run.
The page packages the source and input, sends them to the configured runner or preview frame, and prints standard output plus errors in the output area. Short path. Useful signal.
When something fails, read the first error before changing the whole snippet; many compiler messages are noisy at the bottom but precise near the top, especially when a missing bracket causes a chain of follow-up complaints.
If the first run succeeds, resist the urge to paste the whole project next. Add one feature, one input case, or one Node.js construct at a time, because a runner like this is best at showing the exact moment a simple idea stops being simple.
Try it small
The saved example below is intentionally left unchanged. Run it once as written, then make a small edit and run it again; that gives you a known-good baseline before you test your own idea.
// Reading command-line arguments
const args = process.argv.slice(2);
console.log('Arguments:', args);
// Using console output
console.log('Hello from Node.js!');
// Reading from stdin (provide input in the Input tab)
const readline = require('readline');
const rl = readline.createInterface({
input: process.stdin,
output: process.stdout
});
rl.on('line', (line) => {
console.log('You entered:', line);
rl.close();
});After the sample works, try one edge case that exercises the page's limits. Node is not the browser: window and the DOM are absent, while CommonJS and many runtime globals are normal. That single change often teaches more than pasting a large program and trying to guess which part failed.
Caveats before use
This page is strongest when the problem is small and visible. It is weakest when the problem depends on npm installs, real HTTP servers, file persistence, child processes, and secrets. Two caveats.
- Do not paste secrets, tokens, private URLs, or customer data.
- The environment is intentionally constrained, so a snippet that works here still deserves a local check when compiler flags, packages, server state, or exact versions matter.
- Timeouts are normal for runaway loops. They protect the shared runner.
We deliberately keep the sandbox narrow. That makes the output easier to trust for server-side JavaScript syntax, stdin parsing, async/await, JSON transforms, and shareable snippets, while making it clear when you have outgrown the page.
One practical test: if you cannot explain the snippet in one sentence, split it. The runner is happiest when each run answers a single question, and you will be happier too when the error message points at one idea instead of a pile of guesses.
Where it fits
Three uses come up often: checking syntax while reading docs, reducing a bug report to something another person can run, and trying a small variation before editing a larger project.
For Node.js, the best examples are boring in a useful way. They fit on one screen, they name the input, and they show the exact output you expected or the exact error you got.
A good habit is to keep one saved version that passes, then make the risky change in a copy. When the output changes, you know which line caused it; when it does not, you have learned that the bug probably lives in setup, data, or assumptions rather than the syntax itself.
Questions people actually ask
This FAQ is intentionally mixed: short answers for quick checks, longer notes where Node.js has environment traps. Scan it once before assuming the runner and your local setup behave the same.
What Node.js version does this compiler use?
This editor sends Node.js code to Piston, so the exact version depends on the runtime Piston exposes for the page. That is fine for most syntax and API checks. If you are testing a version-specific feature, such as a newer built-in API, run node --version locally and confirm there too. Version mismatches usually show up as missing APIs or syntax errors.
Can I use require in the online Node.js compiler?
You can use require for built-in Node-style modules that the runner supports, but do not expect npm packages to be installed. For example, testing path.join is reasonable; requiring express is not. If package resolution matters, make a local project with package.json and test the exact dependency versions. That also makes CommonJS versus ES module behavior clearer. If module format matters, check it with the same package.json settings you use locally.
Can I share my Node.js code with others?
Use the Share button when you want someone else to see the same small snippet. Keep the shared code boring: no tokens, passwords, private URLs, or customer data. A good shared example has one input, one expected output, and enough code for another person to reproduce the issue quickly. Include the STDIN value if the program reads input. A short setup script is usually safer than trusting browser state to remember your work.
Does this editor have IntelliSense?
The editor can provide helpful hints, highlighting, and completions, but treat them as editor help rather than a guarantee. The real check is still the output from the runner. If completion suggests an API and the run fails, the runtime version or sandbox support may be different. Trust the error message over the suggestion list. If module format matters, check it with the same package.json settings you use locally.
Can I use ES modules (import/export)?
ES module support depends on how the runner starts your file. CommonJS require is usually the safer choice for quick snippets. If you specifically need import and export behavior, test it in a local Node.js project with the same package.json type setting and file extensions you plan to use. Small module-format differences can change the result. For async tests, a mocked Promise is often cleaner than a blocked network request.
Can I run an HTTP server in this compiler?
No, do not use this page to run a real HTTP server. Listening on ports and accepting network traffic are outside the sandbox’s job. You can still test the logic that would go inside a handler: parse input, build a response object, and check the output before moving locally. Run Express or Fastify on your machine. If module format matters, check it with the same package.json settings you use locally.
Can I use async/await in this Node.js compiler?
Yes, async and await are fine for small examples. They are useful for testing Promise flow, error handling, and timing. Keep in mind that real network calls may be blocked, so use a mocked Promise such as Promise.resolve({ ok: true }) when you only want to test the control flow. Wrap awaits in try/catch when checking failures. For async tests, a mocked Promise is often cleaner than a blocked network request.
Version?
This editor sends Node.js code to Piston, then shows stdout and stderr in the result panel. I would treat that as good enough for syntax checks, but not as a promise about your production version. If a feature depends on a release, run the same snippet locally and check the official release notes. Version mismatches usually show up as syntax errors, missing APIs, or slightly different standard-library behavior.
Can I use packages with Node.js?
Assume package installs are not available here unless the page already loads a library for the demo. That keeps the run predictable and quick. If your example needs a package manager, create a local project and add the dependency there, then use this page only for the small language part. For online testing, replace the dependency call with a tiny mock value and test your own logic around it.
Further reading
Reference pages are better than folklore when an error message gets specific. Start with official docs, then use tutorials for context once the rule is clear.