sync globally installed packages of two node versions installed via nvm

nvm-sync-global-packages.sh

#!/bin/bash
#
# nvm-sync-global-packages (nsgp)

source ~/.nvm/nvm.sh

function change_node_version() {
    nvm use $1 &> /dev/null
}

if [[ -z "$1" ]] || [[ -z "$2" ]]; then
    echo "nvm-sync-global-packages (nsgp)"
    echo "-------------------------------"
    echo "sync globally installed packages of two node versions installed via nvm"
    echo  
    echo "Usage:"
    echo "nsgp <source-version> <target-version>"
    exit 0
fi

NSGP_SOURCE_VERSION=$(change_node_version $1 && node --version)
change_node_version $NSGP_SOURCE_VERSION
NSGP_SOURCE_PACKAGES=$(npm ls -g --depth=0 | grep @ | sed -e 's/[^a-z\-]//g' -e 's/^npm$//g')
NSGP_TARGET_VERSION=$(change_node_version $2 && node --version)

echo "Sync globally installed packages between node $NSGP_SOURCE_VERSION and node $NSGP_TARGET_VERSION:"
echo
echo $NSGP_SOURCE_PACKAGES
echo
read -p "Continue? (Y/N) " -n 1 -r
echo
if [[ $REPLY =~ ^[YyJj]$ ]]; then
    change_node_version $NSGP_TARGET_VERSION
    read -p "Update npm to latest version for node $NSGP_TARGET_VERSION? (Y/N) " -n 1 -r
    echo
    if [[ $REPLY =~ ^[YyJj]$ ]]; then
        npm i -g npm@latest
    fi
    npm i -g $NSGP_SOURCE_PACKAGES
fi