Ask HN: JavaScript libraries to generate graphics

I'm looking for JavaScript libraries that can generate (and perhaps animate) vector graphics. In particular, I'm trying to find a library that can generate patterns such as dots, stripes, etc (there was one on HN a few months ago which I bookmarked but haven't been able to locate). Also happy to take suggestions for libraries or code that's roughly in that graphical vein e.g., dithering, parallax scrolling, other cool 2D effects, etc.