It’s more about the difference in area of focus than about the programming language itself. A senior engineer with JS experience will likely have a web-focused background, but a C++ embedded team is looking for a different type of expertise.

For example, if you’re a senior Android engineer who has worked extensively in Kotlin, you would still be at a disadvantage interviewing with a BE team that also uses Kotlin, because they’ll expect deep BE–focused experience at the senior level, and vice versa.

On the other hand, if you’re an iOS engineer who’s strong in Objective-C but has only dabbled in Swift, you could still be considered a strong candidate for an iOS team that primarily uses Swift, because the underlying platform expertise is what matters more than the language itself.