CodePen - A front end web development playground.
Microsoft Visual Studio - Microsoft Visual Studio is an integrated development environment (IDE) from Microsoft.
JSFiddle - Test your JavaScript, CSS, HTML or CoffeeScript online with JSFiddle code editor.
Eclipse - Eclipse is an open source community, whose projects are focused on building an open development platform comprised of extensible frameworks, tools and runtimes for building, deploying and managing software across the lifecycle.
JS Bin - Sample of the bin:
Rider - Rider is a cross-platform .NET IDE based on the IntelliJ platform and ReSharper.