Mastering JavaScript Functional Programming - Second Edition

Tail call optimization

When is a recursive call not a recursive call? Put this way, the question may make little sense, but there's a common optimization—for other languages, alas, but not JavaScript!—that explains the answer. If the recursive call is the very last thing a function will do, then the call could be transformed to a simple jump to the start of the function without needing to create a new stack entry. (Why? The stack entry wouldn't be required: after the recursive call is done, the function would have nothing else to do, so there is no need to further save any of the elements that have been pushed into the stack upon entering the function.) The original stack entry would then no longer be needed and could simply be replaced by ...