A few examples of getting up and running in classic OpenGL. Currently targetting Emscripten - see Emscripten - Getting Started
https://ariamokr.github.io/SimpleGL/nothing.html
emcc nothing.cpp -o nothing.html
https://ariamokr.github.io/SimpleGL/hello.html
emcc hello.cpp -o hello.html
https://ariamokr.github.io/SimpleGL/triangle.html
emcc triangle.cpp -s LEGACY_GL_EMULATION -o triangle.html
https://ariamokr.github.io/SimpleGL/trianglerotate.html
emcc trianglerotate.cpp -s LEGACY_GL_EMULATION -o trianglerotate.html
https://ariamokr.github.io/SimpleGL/trianglerotatemouse.html
emcc trianglerotatemouse.cpp -s LEGACY_GL_EMULATION -o trianglerotatemouse.html
https://ariamokr.github.io/SimpleGL/trianglerotatekeyboard.html
emcc trianglerotatekeyboard.cpp -s LEGACY_GL_EMULATION -o trianglerotatekeyboard.html
https://ariamokr.github.io/SimpleGL/trianglecolor.html
emcc trianglecolor.cpp -s LEGACY_GL_EMULATION -o trianglecolor.html
https://ariamokr.github.io/SimpleGL/trianglemovebutton.html
emcc trianglemovebutton.cpp -s LEGACY_GL_EMULATION -o trianglemovebutton.html