Recursive string reversal function in javascript?

Question

I'm a pretty experienced frontend engineer with a weak CS background. I'm trying to get my head around the concept of recursion. Most of the examples and purported explanations I can find just aren't explaining it in a way I find easy to understand.

I set myself a task of writing a function that will reverse a string recursively. I know there has to be a base condition (i.e. the solution is found), but I can't figure out how to actually write something like this and could use a demo to study.

Could someone provide a sample function?

Answer 1

Something like:

function reverse (str) {
    if (str === "") {
        return "";
    } else {
        return reverse(str.substr(1)) + str.charAt(0);
    }
}

So the function is recursive as it calls itself to do the work.

Answer 2

A tail recursive version, just for kicks (even though JavaScript doesn't perform tail call elimination):

function reverse(str) {
  function r(s, acc) {
    return (s.length == 0) ? acc : r(s.substr(1), s.charAt(0) + acc);
  };
  return r(str, '');
};