JavaScript Runner
Run JavaScript code instantly in your browser. Supports ES6+, async/await, console output, error handling, and more. Your code runs in a sandboxed iframe and is never sent to any server.
Online JavaScript Code Playground
This JavaScript runner lets you write, test, and debug JavaScript code directly in your browser. No installation, no signup, no configuration. Just write code and hit Run. The code executes in a sandboxed iframe, keeping your page safe while giving you full access to modern JavaScript features.
Features
- Full ES6+ support: arrow functions, destructuring, async/await, classes, generators, optional chaining, nullish coalescing
- Captures
console.log,console.error,console.warn,console.table, andconsole.info - Tabular data display with
console.table()for arrays and objects - Sandboxed execution in an isolated iframe — safe and private
- Error messages with line numbers and friendly formatting
- Execution time measurement for performance testing
- 12 built-in example snippets: array methods, async/await, fetch, regex, and more
- Snippet history saved to localStorage for easy recall
- Keyboard shortcuts: Ctrl+Enter run, Ctrl+Shift+C copy, Ctrl+L clear
- 100% client-side — your code never leaves your browser
How It Works
When you click Run, your code is wrapped in a try/catch block and injected into a sandboxed iframe. The iframe's console methods are overridden to capture output and send it back to the main page via postMessage. This approach gives you real console output while keeping the sandbox fully isolated.
For async code, the runner wraps your script in an async IIFE, so you can use await at the top level. The sandbox waits for all promises to resolve and reports any unhandled rejections.
Use Cases
- Learning JavaScript — experiment with language features and see results instantly
- Quick prototyping — test an algorithm or API call before putting it in your project
- Debugging snippets — isolate and test problematic code outside your application
- Interview prep — practice coding challenges with immediate feedback
- Teaching — demonstrate JavaScript concepts with live code examples