Ranked in these QuestionsQuestion Ranking
Pro Powerful line drawing
Not only Bezier curves but also any lines, shapes, arcs, etc. out-of-the-box.
Pro Convenient API
Clear and concise API with chaining support.
Pro Virtual DOM
Rapid drawing. Only what is necessary is drawn.
Pro Has its own transformation engine
No need to use embarrassing in-browser transformations.
Pro Legacy browser support
Pro Smart layering system
Pro Rich text features
Multiline text support, text measurement, wrap, indent, spacing, align, etc.
Pro Full accessibility (Section 508)
Pro Events support
All browser events are dispatched in the same way in virtual DOM structure also.
Pro Operator overloading
Pro Geometric Tests
An almost-unique feature: can test geometry if contains(), isInside() or intersects() one other object. Offers even hit-testing methods!
Pro Behaviours handled by objects
These features make it easier to create objects that can act autonomously with complex behaviors. This makes Paper a good choice for particle effects and game development.
Pro Object constructors
Elements all have the option of being created with a hash of properties which promotes clean, concise, and contextually local coding practice.
Pro Good for making games
Paper uses a frame based approach to rendering the canvas. This makes it conceptually easier to create objects with animations and behaviors that interact and perform with other objects.
Along with Paper's approach to creating and managing objects this makes Paper especially good for creating applications with complex behaviors with many elements doing different actions at once, and makes it a good choice for making games.
Con Limited to single instance
The code is written in a way that everything is global and limited to a single instance, there is no clean way to use 2 separate instances in the same page
Con Not supported in older browsers
Paper.js runs on top of HTML5 Canvas, which is not supported in older browsers.