Fabric.js vs Hack: What are the differences?

What is Fabric.js? The easiest way to work with HTML5 canvas. It provides interactive object model on top of canvas element. Fabric also has SVG-to-canvas (and canvas-to-SVG) parser. Using Fabric.js, you can create and populate objects on canvas; objects like simple geometrical shapes.

What is Hack? A programming language for HHVM that interoperates seamlessly with PHP. Hack provides instantaneous type checking via a local server that watches the filesystem. It typically runs in less than 200 milliseconds, making it easy to integrate into your development workflow without introducing a noticeable delay.

Fabric.js and Hack can be primarily classified as "Languages" tools.

Fabric.js is an open source tool with 13.2K GitHub stars and 2.14K GitHub forks. Here's a link to Fabric.js's open source repository on GitHub.