turning the list using recursion in javascript

Question

If i have a list and i want to change the list order using the recursion. How can i do that? Is there any simple way or best way to do that?

Here is something that i have think about, how it works:

list = [0,1,2,3,4,5,6,7,8,9];

if if(list.length<1){
    return list;
}else{
    //making list last to first. 
}

should return this: 
[9,8,7,6,5,4,3,2,1,0]

I'm quite new with this recursion, if someone could explain a little bit, how it works. Thanks

Why do you want to use recursion? `list.reverse()` seems simpler. — pablochan, Oct 29 '17 at 22:23
If you need to reverse an array, you could use the [built-in function](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/reverse). If it's an assignment that specifically requires you to use recursion, maybe you should try it yourself. — GolezTrol, Oct 29 '17 at 22:24
Possible duplicate of [How can I reverse an array in JavaScript without using libraries?](https://stackoverflow.com/questions/10168034/how-can-i-reverse-an-array-in-javascript-without-using-libraries) — GolezTrol, Oct 29 '17 at 22:25
Is this a homework question? Have you tried to create a recursive function? You can use a recursive function to create a stack of items and then read them back off the stack in reverse order (i.e. create a push down automaton). — david25272, Oct 29 '17 at 23:08

Ori Drori · Answer 1 · 2017-10-29T22:39:41.907

0

If you really don't want to use Array#reverse, you can over complicate it with a recursion using Array#slice and Array#concat:

var list = [0,1,2,3,4,5,6,7,8,9];

function reverse(list) {
  return list.slice(-1).concat((list.length ? reverse(list.slice(0, -1)) : []));
}

console.log(reverse(list));

edited Oct 29 '17 at 22:39

answered Oct 29 '17 at 22:25

Ori Drori

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Thank you so much for answering. Would be nice, if you could explain a little bit, what "?" means in that code. – user7697691 Oct 29 '17 at 22:56
It's a [ternary operator](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Conditional_Operator). – Ori Drori Oct 29 '17 at 23:10

score 0 · Accepted Answer · answered Oct 29 '17 at 22:41

If the idea is practice recursion, you can see this code, I will explain in comments:

list = [0,1,2,3,4,5,6,7,8,9];

function rev(list, reversed=[]){
  if(list.length === 0){ // if the list is empty, you return the reversed Array
    console.log(reversed)
    return reversed;
  }else{
    reversed.push(list.pop()) // if not empty, you add the last element as the first element of the reversed list 
    return rev(list, reversed) // then you continue the recursion with the list modified
  }
}



console.log(rev(list))

turning the list using recursion in javascript

2 Answers2