so you installed node wrong or did something with sudo

```sudo chown -R $(whoami) ~/.npm```
- `sudo` (because only `sudo` can undo an old `sudo`)
- `chown` - change ownership
- `-R` - recursively
- `$(whoami)` - your username

Or upgrade node 
nvm install lts/dubnium


nvm use 

Express is framework for building web apps in node