jsFiddle is an online development environment and resource for web developers. It allows users to quickly create, edit and share web applications and HTML, CSS, and JavaScript-based code snippets. jsFiddle provides a quick way to prototype, experiment, share, and debug web applications in the browser. It also allows developers to collaborate on projects in real-time and to view changes immediately. The site also features a library of popular frameworks and libraries, including jQuery, AngularJS, React, Bootstrap, and more. jsFiddle also includes a comprehensive set of features for debugging, including a console, DOM inspector, and error/warning log. jsFiddle also has a thriving community of experienced developers who can help answer questions or provide feedback on projects.
jsFiddle allows you to debug and preview the code in real time, while Pastebin is just for storing the code itself.