These days if you want to install a different version of node you do it this way:
First search for your desired package:
brew search node
This might give you the follow results:
heroku/brew/heroku-node ✔
llnode
node@10
nodebrew
leafnode
node ✔
node@8
....
And then install the desired version:
brew install node@8
Also remember that you can install more than 1 node package at the same time, but you cannot have them available at the same time. So if you have the latest/generic node package already installed you need to unlink it first:
brew unlink node
And then you can link a different version:
brew link node@8
For some older node versions (which are keg-only), it might be required to link them with the --force and --overwrite options:
brew link --force --overwrite node@8