OpenGL to WebGL using Emscripten
Demonstrates a colorful triangle using shaders, with support for mouse and touch input:
Demonstrates a textured triangle, using SDL to load an image from a file.
Demonstrates TrueType text, using SDL to render a string into a texture and apply it to a quad.
Demonstrates SGI’s Texfont text, loading a font texture atlas from a .txf file and applying it to a quad, as well as rendering of text strings.
These demos require OS-dependent stuff (keyboard, mouse, touch, text, audio, networking, etc.). SDL provides a cross-platform library to access this.
WebGL provides GPU-accelerated graphics in the browser, and OpenGLES is the subset of OpenGL which most closely matches WebGL.