ZSH function to auto-switch to correct Node version

.zshrc

####
# ZSH function to auto-switch to correct Node version
#   https://gist.github.com/callumlocke/30990e247e52ab6ac1aa98e5f0e5bbf5
#
# - Searches up your directory tree for the closest .nvmrc, just like `nvm use` does.
#
# - If you are already on the right Node version, IT DOES NOTHING, AND PRINTS NOTHING.
#
# - Works correctly if your .nvmrc file contains something relaxed/generic,
#   like "4" or "v12.0" or "stable".
#
# - If an .nvmrc is found but you have no installed version that satisfies it, it
#   prints a clear warning, so you can decide whether you want to run `nvm install`.
#
# - If no .nvmrc is found, it does `nvm use default`.
# 
# Recommended: leave your default as something generic,
# e.g. do `nvm alias default stable`
####

auto-switch-node-version() {
  NVMRC_PATH=$(nvm_find_nvmrc)
  CURRENT_NODE_VERSION=$(nvm version)

  if [[ ! -z "$NVMRC_PATH" ]]; then
    # .nvmrc file found!

    # Read the file
    REQUESTED_NODE_VERSION=$(cat $NVMRC_PATH)

    # Find an installed Node version that satisfies the .nvmrc
    MATCHED_NODE_VERSION=$(nvm_match_version $REQUESTED_NODE_VERSION)

    if [[ ! -z "$MATCHED_NODE_VERSION" && $MATCHED_NODE_VERSION != "N/A" ]]; then
      # A suitable version is already installed.

      # Clear any warning suppression
      unset AUTOSWITCH_NODE_SUPPRESS_WARNING

      # Switch to the matched version ONLY if necessary
      if [[ $CURRENT_NODE_VERSION != $MATCHED_NODE_VERSION ]]; then
        nvm use $REQUESTED_NODE_VERSION
      fi
    else
      # No installed Node version satisfies the .nvmrc.

      # Quit silently if we already just warned about this exact .nvmrc file, so you
      # only get spammed once while navigating around within a single project.
      if [[ $AUTOSWITCH_NODE_SUPPRESS_WARNING == $NVMRC_PATH ]]; then
        return
      fi

      # Convert the .nvmrc path to a relative one (if possible) for readability
      RELATIVE_NVMRC_PATH="$(realpath --relative-to=$(pwd) $NVMRC_PATH 2> /dev/null || echo $NVMRC_PATH)"

      # Print a clear warning message
      echo ""
      echo "WARNING"
      echo "  Found file: $RELATIVE_NVMRC_PATH"
      echo "  specifying: $REQUESTED_NODE_VERSION"
      echo "  ...but no installed Node version satisfies this."
      echo "  "
      echo "  Current node version: $CURRENT_NODE_VERSION"
      echo "  "
      echo "  You might want to run \"nvm install\""

      # Record that we already warned about this unsatisfiable .nvmrc file
      export AUTOSWITCH_NODE_SUPPRESS_WARNING=$NVMRC_PATH
    fi
  else
    # No .nvmrc file found.

    # Clear any warning suppression
    unset AUTOSWITCH_NODE_SUPPRESS_WARNING

    # Revert to default version, unless that's already the current version.
    if [[ $CURRENT_NODE_VERSION != $(nvm version default)  ]]; then
      nvm use default
    fi
  fi
}

# Run the above function in ZSH whenever you change directory
autoload -U add-zsh-hook
add-zsh-hook chpwd auto-switch-node-version
auto-switch-node-version

Ditto @codefulDom. Thanks @callumlocke

@callumlocke you're the Man.
Thanks a lot !

Someone using it can say if it's lightweight? for usage on an low-end machine?

Just discovered others are using this! Thanks @polyglotdev and others for comments, made my day 😄

@maxjf1: while I haven't tried it on a super low-end machine, it's very fast for me, and performance was a main motivation for writing it. While nvm use does take a couple of seconds to run on my machine, this function adds no perceptible overhead for me (and it's designed to avoid calling nvm use unless really necessary).

@callumlocke Works like a charm! Thanks!

Is anyone using the avn + avn-nvm packages? How does this compare? I think it supports .nvmrc too.

Thank you for this!

Very nicely done, but this function unfortunately creates a very noticeable lag in my shell when I switch directories...

Thanks a bunch for taking the time and making this. Cheers

Thanks u! this is dope!

went to use fnm last year. i must say it's faster and less manual 🙏 still thanks a lot for the all the time i used this

Great, thanks!

For others who might have the same issue, on macOS, I had nvm installed, but not configured in zsh, so I had to first add

export NVM_DIR="$([ -z "${XDG_CONFIG_HOME-}" ] && printf %s "${HOME}/.nvm" || printf %s "${XDG_CONFIG_HOME}/nvm")"
[ -s "$NVM_DIR/nvm.sh" ] && \. "$NVM_DIR/nvm.sh"

to my ~/.zshrc otherwiwe I had an error on nvm_find_nvmrc ("command not found: nvm_find_nvmrc")

I ran into an issue with this on MacOS, using an .nvmrc file that was formatted in a Windows env, which appended ^M to the end of the version number and caused it to not work (it always told me to try nvm install). The workaround I found was to brew install dos2unix and replace $(cat $NVMRC_PATH) with $(dos2unix < $NVMRC_PATH) to handle any bad special characters from Windows.

Now it's working great, thank you for this!

This works super fine with me! Thanks for your code it's lit!

Hi! Thanks for this, this is very helpful!
I've added a few code that will show a prompt asking user to install the node version specified in .nvmrc and switch to it automatically.

# Convert the .nvmrc path to a relative one (if possible) for readability
RELATIVE_NVMRC_PATH="$(realpath --relative-to=$(pwd) $NVMRC_PATH 2> /dev/null || echo $NVMRC_PATH)"

# Print a clear warning message
echo "No installed Node version found that satisfies .nvmrc."
echo "  Do you want to install and use the specified Node version($REQUESTED_NODE_VERSION)? (Y/n)"
read -r INSTALL_NODE_VERSION
if [[ $INSTALL_NODE_VERSION =~ ^[Yy]$ ]]; then
  # Install the requested Node version and switch to it
  echo "Installing Node version $REQUESTED_NODE_VERSION..."
  nvm install $REQUESTED_NODE_VERSION
  echo "Node version $REQUESTED_NODE_VERSION installed."
  echo "Switching to Node version $REQUESTED_NODE_VERSION..."
  nvm use $REQUESTED_NODE_VERSION
  echo "Node version switched to $REQUESTED_NODE_VERSION."
else
  echo "Aborted installation. You can manually install the required Node version later."
fi

# Record that we already warned about this unsatisfiable .nvmrc file
export AUTOSWITCH_NODE_SUPPRESS_WARNING=$NVMRC_PATH