What are some alternatives?
HTMLPen - HTMLPen is a free online Visual HTML Editor (WYSIWYG Editor) program allows you visually edit, preview, and run your html code. It is also a powerful online text editor.
JS Bin - Sample of the bin:
CSSDeck - Collection of Awesome CSS and JS Creations to help out frontend developers and designers.
Plunker - Plunker is an online community for creating, collaborating on and sharing your web development ideas.
CodeSandbox - Online playground for React