npm ERR! Class extends value # is not a constructor or null

I had npm problems,While initializing nodejs project,And while installing npm packages.

There are 2 ways to fix it.

FIRST WAY

Change permissions, or ownership of npm.This will work, only if you are having such errorwhen you are not using sudo with npm.link showing how to change npm permission

SECOND WAY

I had this error because of nvm,

1. Uninstall nodejs and npm
2. Uninstall nvm
3. Install nodejs & npm by following command:

sudo apt install nodejs npm