I love using JavaScript for white boarding. It's very forgiving, it's not strongly typed, interviewers are all familiar with it, and large companies almost always allow it. Python is second. I avoid Go, Rust, Java, Scala, etc.. Too verbose.

I do the following in JS:

- General graph algorithms (shortest path, backtracking based)

- Traversals for graphs / trees (depth first, breadth first, iteratively, recursively)

- Heaps (min, max)

- Tries

- Matrix manipulation / traversal. This is a very error prone for a lot of folks even though it looks simple when they need to write it by hand, and I always need to putz around with 5-10 problems.

I have enough exposure to common interview questions that the above is generally enough.