Why does Intellij IDEA shows require undefined with nodejs?

I don't know why my version isn't quite the same (new version? Fresh install?) but my IntelliJ Ultimate didn't have the Node.js Core library @SergioFilhow mentioned.

I had to go to File > Settings > Languages & Frameworks > Node.js and NPM: "Coding assistance for Node.js". After I configured this for my projects, the Node.js Core library showed up under Languages & Frameworks > JavaScript > Libraries.

Open preferences page and select Languages & Frameworks > Javascript > Libraries and select Node.js Globals, just like the image below.

No need to add Node.js core modules (I didn't add and worked the same way)

I had the same problem on windows, with IntelliJ IDEA 15.0.3. The solution was:

File -> Settings -> Languages & Frameworks -> Nodejs and NPM: Click "Enable" button next to Node.js Core library, accept defaults.