"npm start" error with webpack-dev-server

Always good to do

rm -rf node_modules && npm install

Delete webpack-dev-server out of the node_modules directory and run npm install webpack-dev-server

Thanks to a comment, I was able to solve. I tried reinstalling by using npm install. This did not work. I then tried using npm install webpack-dev-server and got an error. It kept saying things like xyz/abc/node_modules/xyz/node_modules/abc/.bin/file exists. Move and try again. I tried that a few times, finally deleted the entire webpack-dev-server directory out of my node_modules directory and reinstalled. It all works now.

By the way, I used this as I was using Lynda.com's "React.js Essential Training". Only including this info for other's who might have this issue.