I had problems installing it Bootstrap as well, so I did:
Install popper.js: npm install popper.js@^1.12.3 --save
Install jQuery: npm install [email protected] --save
Then I had a high severity vulnerability message when installing [email protected] and got this message:
run
npm audit fix
to fix them, ornpm audit
for details
So I did npm audit fix
, and after another npm audit fix --force
it successfully installed!