Is it possible to install NVM when I already have installed nodejs 8 on Ubuntu?

I have installed nodejs 8, I can't run karma tests with angular 1.. As specified on Karma official website Note: Karma currently works on Node.js 0.10, 0.12.x, 4.x, 5.x, 6.x, and 7.x. See FAQ for more info., I guess problem might be in my node version, they recommend to install node via NVM but I already have installed node 8.. is it possible to install nvm and include there my current nodejs?