Why First example of this video didnt return the intened results?

'use strict';

var Person = function (data) { for (var key in data) { this[key] = data[key];
} this.getKeys = function () { return Object.keys(this); } }

var Alena = new Person({ name: 'Alena', role: 'Teacher' });

console.log('Alena\'s Keys:', Alena.getKeys()); // 'this' refers to 'Alena'

var getKeys = Alena.getKeys;

console.log(getKeys()); // 'this' refers to the node process

this seems to be working well but it shows me error like in the video

But at what point error was corrected by changing only to arrow functions?

aren't both function supposed to be working in the exact same way?

I'm bit confused..