Proper Tail Calls

Proper tail call(PTC) is a technique where the program or code will not create additional stack frames for a recursion when the function call is a tail call.

For example, the below classic or head recursion of factorial function relies on stack for each step. Each step need to be processed upto n * factorial(n - 1)

function factorial(n) {
if (n === 0) {
return 1
}
return n * factorial(n - 1)
}
console.log(factorial(5)); //120

But if you use Tail recursion functions, they keep passing all the necessary data it needs down the recursion without relying on the stack.

function factorial(n, acc = 1) {
if (n === 0) {
return acc
}
return factorial(n - 1, n * acc)
}
console.log(factorial(5)); //120

The above pattern returns the same output as first one. But the accumulator keeps track of total as an argument without using stack memory on recursive calls.

The browsers which supports PTC do not generate stack overflow instead shows Infinity with below inputs,

console.log(factorial(10));
console.log(factorial(100));
console.log(factorial(1000));
console.log(factorial(10000));