Question: Is there a JavaScript SDK that allows me to build interactive commenting systems like Figma or Google Docs?

If you're looking for a JavaScript SDK to build interactive commenting systems like Figma or Google Docs, Velt is a strong contender. Velt lets developers add collaboration abilities to their products with features like commenting, in-app notifications, real-time feedback and file sharing. It can handle different collaboration modes, and it can be integrated with different tech stacks and web frameworks, so it's adaptable for use cases like video editors, form builders and task managers.

Another interesting option is Tiptap, a library of content editing and real-time collaboration tools. It includes a commenting system with inline and document comments, offline commenting and webhook event notifications. Tiptap is designed to be flexible with features like a Notion-like editor, AI copywriter, synced whiteboard and collaborative todo list. It can handle real-time collaboration and document management with self-hosted or cloud storage, so it's good for custom content sites and collaborative platforms.

If you're looking for a more text-oriented solution, CKEditor is a modern, feature-rich text editor with more advanced collaborative abilities like real-time editing, comments and revision history. It also has AI-assisted writing abilities and file management and customizable proofreading. CKEditor can be easily integrated with popular frameworks like Angular, React and Vue.js, so it's a good option for creating and editing content.

Although TalkJS is geared more for chat, it also has in-app comments, so it's a broad platform that can be adapted to your needs. With features like real-time message translation, customizable design and multi-platform support, TalkJS can be a good option for adding interactive commenting systems to your apps.