RECURSION

A recursive function typically is formed when a function calls itself by name, as in the following example:

function factorial(num) {
 if (num <= 1) {
  return 1;
 } else {
  return num * factorial(num - 1);
 }
}

This is the classic recursive factorial function. Although this works initially, it's possible to prevent it from functioning by running the following code immediately after it:

let anotherFactorial = factorial;
factorial = null;
console.log(anotherFactorial(4)); // error!

Here, the factorial() function is stored in a variable called anotherFactorial. The factorial variable is then set to null, so only one reference to the original function remains. When anotherFactorial() is called, it will cause an error because it will try to execute factorial(), which is no longer a function. Using arguments.callee can alleviate this problem.

Recall that arguments.callee is a pointer to the function being executed and, as such, can be used to call the function recursively...