Instructions for installing the Node Version Manager on Mac or Ubuntu. The nvm tool can be used to choose a specific version of NodeJs/npm.
Install nvm
$ curl -o- https://raw.githubusercontent.com/creationix/nvm/v0.33.2/install.sh | bash
See https://github.com/creationix/nvm#install-script.
Tips And Tricks
$ nvm ls-remote # lists all of the available versions of NodeJs & iojs
$ nvm ls # list locally installed version
$ nvm install 0.12.3 # install the version 0.12.3 (see ls-remote for available options)
$ nvm use 0.12.3 # switch to and use the installed 0.12.3 version
$ nvm which 0.12.2 # the path to the installed node version
$ nvm current # what is the current installed nvm version
$ nvm alias default 0.10.32 # set the default node to the installed 0.10.32 version
$ nvm --help # the help documents