Sample Code Issue

Hi everyone, I am currently learning coding and just realized if Free Code Camp has a mistake on their sample code. There is a screen shot as you can see, on the red pointed places, the sample code shows us to put QUOTES (""), but when I put QUOTES, the test does not go through. When I take off the quotes, then it goes through and executes successfully.

So my question is, does the sample code have a mistake? Or is the integrated compiler of this website doesn’t accept quotes?

Thanks in advance.

Challenge: Testing Objects for Properties

Link to the challenge:

There is no issue with the sample code. In the editor code, checkProp is a variable which contains a string passed to the the checkObj function. In the example code, the values being checked are literal strings.