in over 10 years of front-end development for non-trivial business applications, i have yet to encounter a scenario where ignorance of bubble sort prevented me from doing my job well.
i can tell you what i value when interviewing a front-end developer - in depth knowledge of cross browser quirks and coding techniques to address said quirks (sans jQuery). someone who can tell me what OOCSS is and why it's beneficial. someone who values every pixel, http request, and div like it was their last and uses them wisely.
i don't discount the value of standard comp sci knowledge, but i get rage face if someone judges my skill as a front-end developer based on how well i answer those types of questions
lastly, ever view source of any Google app? that tells me all i need to know about their idea of a front-end development
So, its less that you know that particular subject, and more what you being able to pick it up is an indicator of.
My point is that most of the very best front-end developers I've met don't have CS degrees. So it seems unfair to penalize them for something they've never been exposed too. There are other ways to assess someones conceptual ability.
Don't you think it's better to hire compiler experts for that exact problem rather than worrying about whether some frontend dude can write his own JS parser?