I understand why people do it, and I certainly wouldn't fault anyone for giving themselves the best possible chance. But at a certain level, it really feels like trying to cheat the system.
In an ideal world, a normal conversation about the technology - your opinions, preferences and experiences regarding it - should be able to reveal what the interviewer needs to know.
I've never been asked these kinds of "knowledge" questions in any interview. Nor have I asked them of any candidate. To me, interviewing is more about finding a fit to the company's and team's culture, than to ascertain if a candidate knows what she is supposed to know. Even if a candidate succeeds in bluffing her way through an interview, she will fall short in the one-month trial period.
I like the one-month trial period. I've walked away twice during the trial period from a company because they were a lot less organized than they did appear during the interviews. Similarly, we have let go of a couple of employees during their one-month trial because they were unable to learn fast enough or were too arrogant.
So you work at this big co. How about you leave your job and come work for us and we may fire you after a month?
The best people are never on the market. You have to get them before they even leave their existing company otherwise someone else will
- one-month trial period - one-year contract - permanent contract
For senior people, the trial period is more of a formality as they are often quick to become productive in the organization. Of course, when after a couple of months it is discovered that the new senior and management do have a fundamental difference of opinion with regard to the future of the organization, professionally, or even personally, the end of the one-year contract is the moment to part ways. This can be initiated by employer, employee, or even both, but that depends on the situation.
Our team consists of experienced and above-average educated developers. We are not looking to attract that one 10x developer, nor do we desperately need a senior developer now. We sort of have too many senior level developers; our retention is high. Anyway, we are looking for similarly educated and experienced people that fit our team, and we offer a culture where such a person can thrive. We prefer to take a while longer to find and grow a great match rather than to gamble on potential talent that might leave again soon.
On the other hand, we do need new developers, particularly specialists, and we have gotten to the point that we are willing to take more risk. But the organization as a whole is still figuring out how to grow beyond a 10 person post-startup development team towards a 100+ person company (we merged with our biggest partner).
During that time both the employee and/or the company can terminate the contract giving a small notice - one week in every country I've worked, but it might be different in other places. In most companies you don't even have access to some (or all) benefits - pension, healthcare, shares... - until you pass that period.
I don't know about your experience, but from where I come from it's almost a fact of life and one of the things you have to weight when looking to move to a new position.
In real life, that googling or checking the docs fits right into the flow of solving the problem. But for an interview it's better to be fresh on as much as you can, even if you haven't been "in it" recently. And it can help a lot with nerves. One or two follow-up questions should help the interviewer figure out whether the person has experience with something or just knows what it is, and as long as the candidate's not pretending to have used things they haven't used, it's hard for me to call preparation cheating.
One fun thing to do as an interviewer is to play the role of a business analyst, asking for how they would implement a particular feature; then, make the requirements purposefully vague (while encouraging the interviewee to ask follow-up questions if they'd like). This is a lot closer to most real-world programming challenges than a detailed discussion of reactive programming.
Studying which opinions are fashionable this time is part of preparation for interview process :).
But more importantly, that kind of interview is strongly biased toward people who are charizmatic, great talker and biased against doers. Especially biased against those more on nerds side.