Npm run serve Error

Running this code have solved my problem on ubuntu 16.04

echo fs.inotify.max_user_watches=524288 | sudo tee -a /etc/sysctl.conf && sudo sysctl -p

Honestly, I don't know why this Error occurred!

But, once I tested it with sudo in terminal, it worked:

sudo npm run serve

or, for development:

sudo npm run dev