I use js objects, of course, which are hash tables.
Would I hire a front-end developer who didn't know that, or didn't know that they had O(1) lookup time? Very possibly. Because there are so many things that are more important than that knowledge when you are actually building software for a business. Things like experience with usability testing, JS/CSS build tools, unit testing and refactoring, a decent eye for graphic design (even if they won't be doing that work themselves), an open-mind and lack of ego -- just off the top of my head, these are all things I'd consider orders of magnitude more important than knowing technical details about hash tables.
Would I hire a front-end developer who didn't know that, or didn't know that they had O(1) lookup time? Very possibly. Because there are so many things that are more important than that knowledge when you are actually building software for a business. Things like experience with usability testing, JS/CSS build tools, unit testing and refactoring, a decent eye for graphic design (even if they won't be doing that work themselves), an open-mind and lack of ego -- just off the top of my head, these are all things I'd consider orders of magnitude more important than knowing technical details about hash tables.