brew node switch version
# install LATEST stable version of node
$ brew install node
# install OLD version of node
$ brew install node@8
# check version of installed node
$ node -v
v10.4.1
# unlink LATEST version of node
$ brew unlink node
# link OLD version of node
$ brew link node@8
# update bash profile to point to OLD version
$ echo 'export PATH="/usr/local/opt/node@8/bin:$PATH"' >> ~/.bash_profile
# or
$ echo 'export PATH="/usr/local/opt/node@8/bin:$PATH"' >> ~/.zshrc
# open a new terminal window and verify version
$ node -v
v8.16.1