JointJS

Feature-rich diagramming toolkit: Highly customizable via community (open-source) and professional (JointJS+) versions; supports custom shapes, inline editing, undo/redo, and more.

Excellent documentation & examples: Extensive guides and demos that speed up development.

Strong support & active community: Professional edition includes dedicated support; users praise responsiveness.

High performance and scalability: Built on SVG—delivers fast rendering even with complex or large diagrams.

Performance issues at scale: Users reported slowdown when adding many links programmatically.

Costly for full features: JointJS+ professional license starts at ~$2,990 (one-time), which may be steep for some.

Formula binding limitations: Data-binding with frameworks can be non-trivial, especially two-way binding.