GoJS - GoJS is a JavaScript library for building interactive diagrams on HTML web pages. Build apps with flowcharts, org charts, BPMN, UML, modeling, and other visual graph types.
mxGraph - mxGraph is a fully client side JavaScript diagramming library - jgraph/mxgraph
jsPlumb - jsPlumb is an advanced, standards-compliant and easy to use JS library for building connectivity based applications, such as flowcharts, process flow diagrams, sequence diagrams, organisation charts, etc. More than just a diagram library.
Konva - Konva is 2d Canvas JavaScript framework for drawings shapes, animations, node nesting, layering, filtering, event handling, drag and drop and much more.
FabricJS - Fabric.js is a powerful and simple Javascript HTML5 canvas library,
Paper.js - Open source vector graphics scripting framework that runs on top of the HTML5 Canvas.