Welcome to JS Playground (hosted at jsplayground.js.org), the ultimate free online JavaScript editor, instant in-browser compiler, and developer REPL. Designed for software engineers, frontend developers, educators, learners, and competitive programmers, our JavaScript playground delivers zero-latency execution directly within your browser runtime with 100% privacy and zero tracking.
Whether you are testing algorithmic problems, experimenting with modern ECMAScript features, debugging asynchronous Promises with top-level await, or prototyping full web interfaces with HTML, CSS, and JavaScript, JS Playground provides a distraction-free, lightning-fast developer environment.
Execute modern JavaScript code instantly without installing Node.js, configuring npm packages, or waiting for remote server containers. Code runs directly inside your browser engine (V8, SpiderMonkey, or JavaScriptCore) delivering true zero-latency performance.
Unlike conventional online code runners that output flat text strings, JS Playground features an interactive console inspired by browser developer tools. Inspect deep nested objects, expand arrays with length badges, visualize structured datasets with console.table(), and trace errors with informative call stacks.
Experience the ergonomics of modern REPL environments. Any expression placed at the end of your script—such as [1, 2, 3].map(x => x * 2) or Math.random()—is automatically evaluated and displayed with a return arrow indicator, completely eliminating the need to write boilerplate console.log() statements.
Write asynchronous JavaScript naturally. Top-level await is enabled by default, allowing you to fetch data from public REST APIs using await fetch('https://api.example.com') without wrapping your code inside an asynchronous function or immediately-invoked function expression (IIFE). Full support for Web APIs including setTimeout, setInterval, Promise, URL, and Crypto is included.
Test quick one-line expressions or inspect variables dynamically using the built-in command prompt located at the bottom of the console card. Use the Up and Down arrow keys to cycle through your previous evaluation history.
Toggle seamlessly between JS Mode for focused JavaScript logic testing and Web Mode for complete web component prototyping with separate HTML5, CSS3, and JavaScript tabs alongside a real-time sandboxed live preview.
Your source code never leaves your device. All compilation, execution, and evaluation occur strictly within your browser's local sandbox. No code is stored on, transmitted to, or monitored by any remote backend server.
Type or paste your code directly into the left editor pane. Click the Run button or press Ctrl + Enter (Windows/Linux) or Cmd + Enter (macOS) to execute your code immediately.
You can make direct HTTP network requests to any CORS-enabled API endpoint:
const response = await fetch('https://jsonplaceholder.typicode.com/todos/1');
const todo = await response.json();
console.log(todo);
Visualize arrays of objects in a clear tabular grid by calling console.table(data). This makes inspecting complex collections intuitive and readable.
Use the upload button in the editor header to open local .js, .ts, .json, or .html files. The built-in format button automatically cleans and indents your code.
console.clear() directly in your code or REPL prompt.
JS Playground also features full support as a TypeScript Playground (accessible at jsplayground.js.org/typescript-playground). Write, compile, and execute TypeScript code online with instant output. Test interfaces, type aliases, generics, enums, decorators, and modern TypeScript features directly in your browser with zero build setup.
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