Problem with "Profile Lookup" JS Exercise

I am having a lot of trouble with the Profile Lookup exercise, I try not to go to the forums for most exercises since the temptation to copy code is inevitable. However, whenever looking through discussions pertaining to this exercise with hints instead of the downright answer, I see most people using the hasOwnPropety function. I don’t understand how people got the idea in using this method when it’s not mentioned in the exercise itself, nor do I remember using it in previous exercises. Could someone explain this then point me in the right direction?

If you back up 10 challenges, you will see which first introduces hasOwnProperty