Run JavaScript Code Online

Execute JavaScript code right in your browser and see the results. Save, share, and collaborate on your JavaScript code online. Detect and fix JavaScript errors with built-in syntax highlighter and validator. Learn JavaScript programming with an extensive and hand-picked database of JavaScript code examples. No browser plugins or additional desktop software are needed for using the Online JavaScript code runner. It's free.
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Run JavaScript Code Online

ReqBin has been running JavaScript code in the browser since 2022. More than a million developers have used ReqBin since. Paste a script into the editor, press Execute, and the JavaScript runner returns whatever your code writes to the console. Your code runs inside your own browser and is not sent to a server.

  • Write and test JavaScript code online
  • Run JS code directly in your browser — nothing is installed
  • Share and discuss your JavaScript code snippets online
  • Built-in JavaScript syntax highlighter and validator

What is JavaScript?

JavaScript is a high-level programming language that allows you to execute complex scenarios on web pages, such as making requests to third-party API services, dynamically creating content on a page, displaying interactive maps, animating 2D/3D graphics and games, and playing music right in the browser.

JavaScript code can be embedded directly into HTML in the <script> tag, or linked to an HTML page from an external URL.

JavaScript Code Example
<html>
   <head>
       <title>JavaScript Code Example</title>
       <script src="app.js"></script>
   </head>
   <body>
      <h1 id='title'>Title</h1>
      <script>
         document.getElementById('title').innerHTML = "My Title";
       </script>
   </body>
</html>

JavaScript is an asynchronous and single-threaded programming language and supports event-driven, functional, and imperative programming styles. JavaScript has built-in methods for working with text, numbers, regular expressions, dates, and the browser's document object model, and is ECMAScript compliant.

Along with writing interactive web pages, JavaScript is often used to write back-ends for web servers (thanks to Node.js), allowing developers to have almost the same technology stack for both the UI and server-side development.

What are the advantages of JavaScript?

  • JavaScript is fast and works in the user's browser.
  • JavaScript is easier to learn than lower-level languages such as C++.
  • JavaScript is cross-platform; your code will work equally well in browsers on Windows macOS and Linux.
  • JavaScript is extremely popular, and you can quickly find any answers to your JavaScript questions.
  • JavaScript is client-side, and a well-designed JavaScript application can significantly reduce the load on your web server by performing some of the computation directly in the browser.

How to run JavaScript code online?

Paste your script into the editor above and press Execute. The JS runner returns everything your code writes with console.log(), plus any error the script throws. Nothing is installed: no desktop app, no browser plugin, no account.

Your code runs in the browser rather than on a server, so it never leaves your machine. The runner executes standalone scripts, not web pages: the document object from the HTML example above is not available here, and neither are window and alert. Node.js APIs such as require and fs are not available either; use the online Node.js runner for those.

Syntax highlighting marks errors as you type, before you press Execute.

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