How this works in nodes global

default-binding-this-nodejs.js

(function (exports, require, module, __filename, __dirname) {
  //****Your code starts here****//
  var city = 'Karur';
  console.log(this.city); // undefined
  console.log(city); //Karur
  //****Your code ends here****//
});

var args = [self.exports, require, self, filename, dirname];
return compiledWrapper.apply(self.exports, args);