MxGraph is a Javascript library that aims to provide diagram creating tool and interactive drawing capabilities in web-based interface. Target applications are Web based applications that require workflow/BPM, diagram, network, or general graph editing to be available in-place on a Web page. The application is available for free for non-commercial use, but pricing for commercial license start from $3'000 USD. You can find a working demo on the website with some samples diagrams so you can see the different features in place.

The interface is pretty neat with a toolbar in the left including the different drawing options and shapes, in addition the copy paste, undo redo, connection between objects, group and ungroup, zoom, outline view, debug window, and finally you can save, print or view as image. Simply in Javascript