Javascript: Linked object/list function returning undefined

Question

I am trying to return the length of a linked object(list). However, the function I wrote doesn't return anything.

let linkedObject = { value: 1, rest: { value: 2, rest: { value: 3, rest: null } } }

function countDepth(liste, count = 0){
        if (liste == null) return count
        else {
            count ++
            liste = liste.rest
            countDepth(liste, count)
    } 
}

console.log(countDepth(linkedObject))```

expected output:
'3'
actual output:
'undefined'

Jack Bashford · Accepted Answer · 2019-08-25 23:39:47Z

1

You need to return the recursive call:

return countDepth(liste, count);

Also note it can be optimized and made more concise like so:

const countDepth = (l, c = 0) => !l ? c : countDepth(l.rest, ++c);

answered Aug 25, 2019 at 23:39

Jack Bashford

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3 Comments

Filmmaker Over a year ago

This worked, but you can explain why for future reference?

Jack Bashford Over a year ago

Because if the if statement isn't fulfilled, there are no returns within that execution of the function, so undefined is returned.

Filmmaker Over a year ago

Ohh..I think that makes sense. The first iteration returns the second iteration, which returns the third and so on...all the way to the actual answer. Without the second return statement, this chain would be broken and the actual answer would be left abandoned.

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