1. A Static Type Checker for JavaScript

  2. Get started with Google Chrome's built-in web developer tools.

  3. Examine, edit, and debug HTML, CSS, and JavaScript on the desktop and on mobile.

  4. SplineTech JavaScript Debugger. Debug JavaScript.

  5. Easy debugging for mobile web. Remote web inspector with zero configuration.

  6. TypeScript allows developers to compile a superset of JavaScript to plain JavaScript on any browser, host, or operating system.

  7. Build better apps with Xamarin Studio.

  8. Cross platform development tools for native iOS, Android, desktop and server applications.

  9. Opera Dragonfly is a cross device, cross platform debugging environment for the Opera browser-debug JavaScript, inspect and edit CSS and the DOM, and view any errors on your mobile or computer.

  10. Code Cola is a chrome extension to editor online pages' style visibility.

  11. Browsersync makes your tweaking and testing faster by synchronising file changes and interactions...

  12. Ghostlab allows you to test out a newly developed website on a variety of browsers and mobile devices at the same time. To get started, simply drag the web address to the Ghostlab system and press the play button. Read more about Ghostlab.