Javascript Recursion

Question

Very simply, what is javascript recusion? More specifically, Can anyone show some small code snippets where it could be applied(please do not use the factorial, egg chicken: thanks 😐), and where not, with an explanation of why

Answer 1

First off: Anything you can do with recursion you can do without and the other way around, so pick what works best. Some examples:

Say you have some function that takes 2 numbers a and b and you want to make sure a is always smaller than b:

function something(a, b){
if(a > b) return something(b, a);
// do something
}

Not saying it's good practice but I've seen it a lot.

Say you have a function that sends money but you can only send 1000€ max:

function send_money(amount){
while(amount > 1000){
send_money(1000);
amount -= 1000;
}
// send the rest of the money
}

Those are some of the more simple examples; more typical examples are usually a bit harder.

Say you have a network of cities and you want to visit them all:

function visit(city){
take_photo(city);
for(let neighbor of city.neighboring_cities()){
if(not_seen(neighbor))
visit(neighbor);
}
}

That's venturing into graphs and other data structures though.

(1/2)

Answer 2

In general recursive functions tend to be less efficient than non-recursive ones, so if performance is a concern, then you should prefer non-recursion.

Some programming languages try to optimize some recursive functions (tail recursion, stream fusion), but as far as I know Javascript isn't one of them.

A general rule is to worry about performance last, so pick whatever code looks nicer. The third code snippet would look pretty horrible and 3 times as long without recursion, for example: Every city may have many neighbors and each of them has many neigbors and so on, so you get this branching out behaviour; that's where recursion really works well.

(2/2)

Answer 3

Schindlabua Thanks.😊😊😊😊