How to automate the nvm use script

tl;dr

• If you have multiple projects using multiple Node Js versions, this will help you a lot.
• I assume you use nvm (Node Version Manager) to handle node versions
• By adding a script into your ~/.bashrc or ~/.zshrc you can automate the nvm use script.

How to automate the script nvm use in Bash

Automatically call nvm use

Put the following at the end of your $HOME/.bashrc:

cdnvm() {
    command cd "$@";
    nvm_path=$(nvm_find_up .nvmrc | tr -d '\n')

    # If there are no .nvmrc file, use the default nvm version
    if [[ ! $nvm_path = *[^[:space:]]* ]]; then

        declare default_version;
        default_version=$(nvm version default);

        # If there is no default version, set it to `node`
        # This will use the latest version on your machine
        if [[ $default_version == "N/A" ]]; then
            nvm alias default node;
            default_version=$(nvm version default);
        fi

        # If the current version is not the default version, set it to use the default version
        if [[ $(nvm current) != "$default_version" ]]; then
            nvm use default;
        fi

    elif [[ -s $nvm_path/.nvmrc && -r $nvm_path/.nvmrc ]]; then
        declare nvm_version
        nvm_version=$(<"$nvm_path"/.nvmrc)

        declare locally_resolved_nvm_version
        # `nvm ls` will check all locally-available versions
        # If there are multiple matching versions, take the latest one
        # Remove the `->` and `*` characters and spaces
        # `locally_resolved_nvm_version` will be `N/A` if no local versions are found
        locally_resolved_nvm_version=$(nvm ls --no-colors "$nvm_version" | tail -1 | tr -d '\->*' | tr -d '[:space:]')

        # If it is not already installed, install it
        # `nvm install` will implicitly use the newly-installed version
        if [[ "$locally_resolved_nvm_version" == "N/A" ]]; then
            nvm install "$nvm_version";
        elif [[ $(nvm current) != "$locally_resolved_nvm_version" ]]; then
            nvm use "$nvm_version";
        fi
    fi
}
alias cd='cdnvm'
cd "$PWD"

This alias would search 'up' from your current directory in order to detect a .nvmrc file. If it finds it, it will switch to that version; if not, it will use the default version.

How to automate the script nvm use in zsh

Calling nvm use automatically in a directory with a .nvmrc file

Put this into your $HOME/.zshrc to call nvm use automatically whenever you enter a directory that contains a .nvmrc file with a string telling nvm which node to use:

# 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

Notes

• This script will run every time you load a directory on your terminal.
• This will ovoid Node Js versions inconsistencies.

Happy coding! :)