Some time ago I have shown you how to run fnm use automatically using direnv (here). That solution has one problem however - you need to create .envrc file near each .nvmrc.

As you already have .nvmrc wouldn’t it be nice if fnm use were run when you enter your folder with .nvmrc in it. Doing it is quite simple using bash:

function nvmrc_check() {
  if [[ -f .nvmrc ]]
  then
    fnm use
  fi
}

function cd() {
  builtin cd "$@"
  nvmrc_check
}

nvmrc_check

nvmrc_check function checks if there is .nvmrc file and runs fnm use (feel free to use nvm if it is a weapon of your choice). function cd() overrides cd command to run default cd command and run nvmrc_check. In addition you need to run nvmrc_check on start as your shell might start in the folder you need.

This is solution has one problem however. If you cd to folder that does not have .nvmrc (but for example parent folder has) fnm use will not run. You can improve this script to check for .nvmrc file back to parent and etc but I will leave this task for you as exercise.