(Note: be sure to tell emacs to use the clangd version you installed on your system)
(setq lsp-clangd-binary-path "/usr/bin/clangd")

Emscripten is a complete compiler toolchain to WebAssembly, using LLVM, with a special focus on speed, size, and the Web platform.

— emscripten.org

If you happen to want programming in C/C++ for the web,
if you happen to live inside of emacs,
you are probably using clangd and emscripten.

As you may know clangd is most useful when a compile_commands.json database file is generated in your project, you have several options to generate one, but all in all, you generally have to use a software build system;
this is how I began using CMake.

At the root of your project, you have to specify the build process in a CMakeLists.txt file, here we provide a basic file which tell CMake to:

• require version 3.8
• name the project "someProjectName"
• ensure the compiler uses C++17
• add "test" as an executable, compiled from the single file src/test.cpp
• set some linker-specific flags for the target "test" (these flags are related to emscripten)

# cmake_minimum_required(VERSION major.minor)
cmake_minimum_required(VERSION 3.8)

#project(<NAME>)
project(someProjectName)

set (CMAKE_CXX_STANDARD 17)

add_executable(test src/test.cpp)

set_target_properties(
  test
  PROPERTIES
  LINK_FLAGS
  "--bind -s WASM=1 -s MODULARIZE=1 -s ALLOW_MEMORY_GROWTH=1 -s WASM_ASYNC_COMPILATION=0 -s BINARYEN_ASYNC_COMPILATION=0 -s ENVIRONMENT=shell"
)

Emscripten, which allows us to compile C++ to wasm, acts as a kind of wrapper around your software build system. Once you've installed it, if you are using CMake, the recommended way of doing is: