# NVM
export NVM_HOME="$HOME/.nvm"
if [[ -f "$NVM_HOME/nvm.sh" ]]; then
    source "$NVM_HOME/nvm.sh"
fi

# NVM TAB COMPLETION
if [[ -f "$NVM_HOME/bash_completion" ]]; then
    source "$NVM_HOME/bash_completion"
fi

# NPM TAB COMPLETION
if npm -v >/dev/null 2>&1; then
    . <(npm completion)
fi

This commands works considering that you are on a linux terminal. Change the variable $NVM_HOME to the path that your NVM is installed.

Sourcing NVM, adding NVM Tab Completion and NPM Tab Completion

Bash