Quick note, Lazy Foo's SDL tutorials haven't been fully updated to SDL2 yet. This site has good tutorials though http://twinklebeardev.blogspot.co.uk/p/sdl-20-tutorial-index.html?m=1

Ah good point, it is worth mentioning that Emscripten provides SDL 1.x (and soon SDL 2.0). However, since the emscripten version of the SDL API has been tweaked to run in a mobile browser (i.e touch events) and is already 3D accelerated, it is likely to stick around for many years to come (and will almost certainly still outlive commercial proprietary products like Unity).