Welcome to HCODX Online Compiler
Quick Start:
Ctrl+Enter Run code
Ctrl+S Save / Download
Ctrl+L Clear output
Select a language and start coding.
Compile and run JavaScript code online instantly with HCODX. Our free cloud-based JavaScript compiler supports real-time execution, standard input, syntax highlighting, and code download. No installation or configuration required. Start coding in JavaScript now.
Run JavaScript instantly without installing any IDEs or configuring environments. Our cloud-based JavaScript handles libraries, runtimes, and dependencies automatically so you can focus on writing code.
Whether you are studying algorithms in JavaScript, practicing data structures in JavaScript, or exploring functional programming, our tool provides real-time stdout/stderr feedback with interactive standard input support.
HCODX is a free online compiler and code runner: write code in your browser, execute it on a cloud sandbox, and interact with your program through a live terminal. Students use it for coursework and interview practice; developers use it to test snippets in 85+ languages without setting up a local environment.
More code is written in JavaScript than in any other language — it has topped Stack Overflow's developer survey for over a decade and runs on virtually every website in existence. Netflix, PayPal, and Airbnb ship production JavaScript on both the client and the server, and recent ECMAScript editions keep adding practical features like optional chaining, top-level await, and array grouping. On this page your code executes on a server-side V8 engine with a genuinely interactive terminal: console.log output appears the instant it's produced, and readline prompts pause mid-run and wait for you to type — much like a REPL session on your own machine, with no Node install and no setup.
const readline = require("node:readline");
const rl = readline.createInterface({ input: process.stdin, output: process.stdout });
rl.question("Enter a word: ", (word) => {
const flipped = [...word].reverse().join("");
console.log(`Reversed: ${flipped}`);
console.log(flipped === word.toLowerCase() ? "That's a palindrome!" : "Not a palindrome.");
rl.close();
});Verify a snippet from MDN or Stack Overflow before it goes into your web app, drill array methods, closures, and promise behavior for front-end interviews, or run bootcamp homework without touching a terminal setup. Coding-challenge sites feed input through stdin, and the live terminal here reproduces that exactly — so a HackerRank JavaScript solution behaves the same way during practice as it does during the real assessment. Regex testing, date math, and JSON transformations all run instantly. HCODX is a free online JavaScript editor, runner and interpreter — an IDE-grade compiler and playground to write and run code online, execute code with live output and live preview, no downloads or web server required.
Yes. The code runs in a live terminal session, so readline (or reading process.stdin directly) genuinely blocks until you type a line and press Enter. Multi-prompt programs, guessing games, and menu loops all work — there's no requirement to pre-paste input before clicking Run.
Server-side. Your code executes on the V8 engine via a Node-based runtime, so browser globals like document, window, alert, and fetch-into-the-DOM patterns aren't available. Everything language-level — classes, generators, async/await, destructuring, Map/Set, template literals — works exactly as it does in any modern engine.
No — the sandbox doesn't run npm install, so third-party packages aren't available. Built-in modules (fs, path, crypto, util) and the full JavaScript standard objects are. For algorithm practice, interview prep, and language experiments that's rarely a limitation; for framework work you'll want a local project.
Your current code will be replaced with the default sample. This cannot be undone — download your code first if you want to keep it.
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