Reach nested array item using recursion - javascript

Question

I'm trying to reach the center of a nested array using recursion. This is part of a larger problem I'm trying to solve. I'm sure the solution is somewhat elementary. I've been learning JS/web dev and am stumped.

Here's my code:

var j = [[[["hey!"]]]];

function getNested(obj) {
for (var i = 0; i < obj.length; i++) {
    if (Array.isArray(obj[i])) {
        obj = obj[i];
        getNested(obj);
    } 
    return obj[i];
  } 
}

The function is supposed to return the 'hey!' string, but I can't seem to get it right.

Why is there a for loop if you'll only ever find the first innermost nested element and return it? How is your code recursive? — millimoose
– millimoose, Commented Sep 28, 2013 at 20:24
What if there is more than one element in any of the nested arrays? — Kevin Bowersox
– Kevin Bowersox, Commented Sep 28, 2013 at 20:25
I don't see a place where getNested calls itself, be it directly or through mutual recursion. — Matt Ball
– Matt Ball, Commented Sep 28, 2013 at 20:25
What is findType? If you're looking for recursion, switch out that line for return getNested(obj) — Cᴏʀʏ
– Cᴏʀʏ, Commented Sep 28, 2013 at 20:25
I can't see recursion in your code. getNested() should call itself somewhere. What if your array looks like that ["hey1",[[["hey!", "hey2"]]]] for example? What should be returned? — biera
– biera, Commented Sep 28, 2013 at 20:31

Cᴏʀʏ · Accepted Answer · 2013-09-28 20:34:56Z

3

You are close, just switch out the findType(obj) for return getNested(obj[i]). This will give you a recursive function that drills down into the array until the item in the array is not another array. Also, the for-loop was unnecessary, given your example input.

This will only work if your nested arrays have exactly one element. Others have expressed this in the comments.

var j = [[[["hey!"]]]];

function getNested(obj) {
    if (Array.isArray(obj)) {
        return getNested(obj[0]);
    } 
    return obj;
}

var str = getNested(j);
console.log(str); // "hey!"

jsFiddle Demo

edited Sep 28, 2013 at 20:34

answered Sep 28, 2013 at 20:28

Cᴏʀʏ

108k20 gold badges169 silver badges200 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Udo Klein · Accepted Answer · 2013-09-29 10:24:05Z

2

There is no need for recursion, a simple while loop will already do the trick

var j = [[[["hey!"]]]];

function getNested(obj) {
    while (Array.isArray(obj)) { obj = obj[0]; } 
    return obj;
}

var str = getNested(j);
console.log(str); // "hey!"

The recursive implementation has the nice property that it is purely functional though if you rewrite it like so:

var j = [[[["hey!"]]]];

function getNested(obj) {
    return Array.isArray(obj)? getNested(obj[0]): obj;
}

var str = getNested(j);
console.log(str); // "hey!"

Still its performance would be worse though.

edited Sep 29, 2013 at 10:24

answered Sep 28, 2013 at 21:24

Udo Klein

6,9401 gold badge39 silver badges63 bronze badges

3 Comments

Udo Klein Over a year ago

It uses a loop instead of recursion. Thus it should perform significantly better for deeply nested arrays.

Ilya Over a year ago

May be you shoud write There is NO need for recursion

Udo Klein Over a year ago

The recursive solution has the only advantage that it could be written in a more compressed way like so: function getNested(obj) { return Array.isArray(obj)? getNested(obj[0]): obj; } Still its performance would be worse.

Collectives™ on Stack Overflow

Reach nested array item using recursion - javascript

2 Answers 2

Comments

3 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

3 Comments

Your Answer

Sign up or log in

Post as a guest

Related