For people that just want to install packages that are not included in the Arch distro, and don't have the knowledge or time to review PKGBUILD files:

Have a look into the Guix package manager. It works fine on top of Arch, and Guix has 31,000 packages now. Great for cross-language development and also suitable for early sharing of projects. npm support is a bit weak though, but packages written in Python, Rust, or functional languages are well represented.