This is a feature that allows the runtime to recognise that it can discard the intermediate stack frames since the result to the final call can simply replace that entire set of frames. However if you want to loop over an indeterminate-size list of URLs to find out when each page last changed, it seemed hard -- until I remembered tail recursion, which is pretty simple -- but I don't see many people talking about it. Tail Recursion. Thiery Michel February 12, 2018 ... And in case you wonder, the recursive version is slower than the loop version - at least in JavaScript. This way we let the compiler know that the stack frame of the current function need not be retained. JavaScript recursive functions need to keep track of where they were called from each time, so they can resume at the correct point. Probably in the first few classes of any beginner courses. Tail calls in Javascript Now what I said above is only technically true if the runtime your code is executing in implements something called tail-call optimisation. As you might have noticed we’re now passing two arguments to it: the number we want to calculate the next factorial of (n - 1) and the accumulated total, which is n * total. The ideas are still interesting, however and explained in this blog post. The head is the first element of the list, the tail is the list composed of the list minus the head. Moreover, the recursive call must not be composed with references to memory cells storing previous values (references other than the … So I thought I'd write it up. Update 2018-05-09: Even though tail call optimization is part of the language specification, it isn’t supported by many engines and that may never change. Recursion is one of the topics that everyone covers, no matter which programming language you are learning. I love JavaScript. I don't know why but I do. For a detailed overview of what constitutes tail position, there’s a really nice dive into that in in this post . Tail Recursion: The idea of a tail recursion is that recursive call is the last operation we perform on a non base case. Tail recursion is a special way of writing recursive functions such that a compiler can optimize the recursion away and implement the algorithm as a loop instead. Tail-recursion is a form of recursion in which the recursive calls are the last instructions in the function (that's where the tail part comes from). Kristijan Pajtasev Oct 22 ・3 min read. ... which makes it tail recursive. All About Recursion, PTC, TCO and STC in JavaScript. In functional programming when we run functions recursively over lists we like to model the list as a head and a tail. Understanding Recursion, Tail Call and Trampoline Optimizations. Recursion isn't a matter of performance, but of expressiveness. Tail recursion in JavaScript. Functional Programming: lists & recursion. 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