I’ve also ended interviews as a candidate on the phone myself. They asked a question that I didn’t’ have the answer to and I told them that I didn’t know. The next 2 questions were in that same direction, with them knowing that I’d already said I wasn’t particularly fluent in that area but they kept on. At that point I said, “Let’s just stop here. We both know that I’m not doing well answering your questions and to be honest, that you’re restating the same topic after being told that already I don’t know probably means we wouldn’t be a good fit.” Too many people forget that it’s a two-way street and they seems shocked that anyone would actually end their interview.

A less confrontational way to address this is to ask your boss to help you understand why he thinks you can handle these tasks. The other part of this discyion is to help clarify expectations. Who knows, you may find that they really don’t expect you to handle this, but you’re there only hope at the moment. Do your best.

Even if you were given tasks you can easily perform, you always want to know what is expected of you from your immediate supervisor. I always suggest focusing on meeting his expectations. It will make your job more successful in the short and long-term.

Since you’re new to the job, there are many aspects I think you’re misunderstanding and putting too much pressure on yourself because so far, you’ve never mentioned anyone complaining or giving you negative feedback.

Before going to the interview, you can send a note (I would prefer that over a phone call) that you had applied for this position and you are appearing for the interview. You can express your concern anyway about conflict-of-interest but more likely than not he will understand the situation himself and ideally should keep himself out of decision making process.

I will disagree with Rishabh on this one, it’s only when I started with JavaScript did I truly come to appreciate the design decisions that are made in any programming language.
JavaScript taught me a whole lot of semantic concepts. Be it the prototypal school of inheritance, or functional programming concepts like closures, functions as first class citizens, higher order functions.
Yes, JavaScript did have a bad reputation a while back, but let bygones be bygones. Investing sometime – emphasis on the fact that you need to invest time in learning the language, the design decisions and especially it’s good parts will enrich your repertoire.
Today JavaScript is pervasive, node.js in the server, EcmaScript 5.1 in the browser, databases all were powered by this language. So, the investment is well worth the gains.

Back-End Developers concentrate on what goes on behind the scenes of a website. These are the people who build the databases that host the site’s content and implement the technologies that runs its search and e-commerce capabilities. Focused more on the website’s responsiveness and speed than what its pages look like, they’re skilled in languages such as Python and PHP, and frameworks like Django and Ruby on Rails. Their pay ranges from $43,000 to $116,000, PayScale says, with a median of $75,000.