#WebStorm - enable Nodejs and npm

When you use WebStorm and see this error: unresolved variable or type module when you hover over module like the screenshot below.

sayHello = function (name) {
  return 'Hello ' + name + '!';

module.exports = sayHello;

Nodejs npm Unresolved variable or type module
Unresolved variable or type module
You have to enable Node.js core library - node interpreter on WebStorm preferences here like the screenshot below. 

Then, WebStorm will be able to recognize module.

Thanks for reading!