Automatic node switching for zsh and bash

.bashrc

# place this at the end
# ••••••••••••••••••••••••••••••••••••••••

_enter_dir() {
    local git_root
    git_root=$(git rev-parse --show-toplevel 2>/dev/null)

    if [[ "$git_root" == "$PREV_PWD" ]]; then
        return
    elif [[ -n "$git_root" && -f "$git_root/.nvmrc" ]]; then
        nvm use
        NVM_DIRTY=1
    elif [[ "$NVM_DIRTY" == 1 ]]; then
        nvm use default
        NVM_DIRTY=0
    fi
    PREV_PWD="$git_root"
}

export PROMPT_COMMAND=_enter_dir
#export PROMPT_COMMAND="$PROMPT_COMMAND;_enter_dir"  # use this if PROMPT_COMMAND already defined

.zshrc

# place this after nvm initialization!
# ••••••••••••••••••••••••••••••••••••••••

autoload -U add-zsh-hook
load-nvmrc() {
  local node_version="$(nvm version)"
  local nvmrc_path="$(nvm_find_nvmrc)"

  if [ -n "$nvmrc_path" ]; then
    local nvmrc_node_version=$(nvm version "$(cat "${nvmrc_path}")")

    if [ "$nvmrc_node_version" = "N/A" ]; then
      nvm install
    elif [ "$nvmrc_node_version" != "$node_version" ]; then
      nvm use
    fi
  elif [ "$node_version" != "$(nvm version default)" ]; then
    echo "Reverting to nvm default version"
    nvm use default
  fi
}
add-zsh-hook chpwd load-nvmrc
load-nvmrc