Update Node, reinstall global packages, and remove older versions. To be placed in shell profile.

nvm-clean-install.sh

# Automate installing a new version of node, re-installing global
# node modules, and uninstalling older node versions.
#
# Depends on nvm, semver, and python3.
#
# semver will be auto-installed if it doesn't exist yet.
#
# If a single arg is given:
#
#   1. Install the new node version given as the first arg.
#   2. Switch to the new node version.
#   3. Re-install global npm modules with the new node.
#
# In all cases, node versions where there is a newer one with
# the same major version already installed will be removed.
#
# For example, if the following node versions are installed:
#
#   8.17.0
#   10.5.0
#   10.8.0
#   10.18.1
#   12.13.0
#   12.14.1
#
# Then 10.5.0, 10.8.0, and 12.13.0 will all be uninstalled.
# The rest will be left alone.
nvm-clean-install() {
  if [ "$#" -eq 1 ]; then
    nvm install "$1" --reinstall-packages-from=$(node --version) --latest-npm
  fi  

  if ! command -v semver > /dev/null 2>&1; then
    npm i -g semver
  fi  

  local NODE_DIR=$NVM_DIR/versions/node
  local REMOVE_VERSIONS=$(semver $(ls $NODE_DIR) | tail -r | python3 -c 'import sys; vers = map(lambda x: x.strip(), sys.stdin.readlines()); seen = set(); vers = filter(lambda x: x.split(".")[0] in seen or seen.add(x.split(".")[0]), vers); print("\n".join(vers))')

  if [ ${#REMOVE_VERSIONS[@]} -ne 0 ]; then
    echo "uninstalling old node versions..."
    for v in $REMOVE_VERSIONS; do
      nvm uninstall $v
    done
  fi  
}