I have an object with nested object:

let list = {
  value: 1,
  next: {
    value: 2,
    next: {
      value: 3,
      next: {
        value: 4,
        next: null
      }
    }
  }
};

I need to return all key: value of list and I must use recursion. I have tried to push the nested object to the local variable in the function, but it fails in the second iteration because the names are different.

Here is the function:

function printList(list){
  let nested = {};

  if(list.hasOwnProperty('next')) {
      nested = list.next;
      printList(nested);
  } else {
    return nested;
  }
}

Is there a way to solve it with recursion?

It should return the value properties. In this case

1
2
3
4

I have an object with nested object:

let list = {
  value: 1,
  next: {
    value: 2,
    next: {
      value: 3,
      next: {
        value: 4,
        next: null
      }
    }
  }
};

I need to return all key: value of list and I must use recursion. I have tried to push the nested object to the local variable in the function, but it fails in the second iteration because the names are different.

Here is the function:

function printList(list){
  let nested = {};

  if(list.hasOwnProperty('next')) {
      nested = list.next;
      printList(nested);
  } else {
    return nested;
  }
}

Is there a way to solve it with recursion?

It should return the value properties. In this case

1
2
3
4

• javascript
• object
• recursion

Share Improve this question Follow edited Sep 26, 2019 at 10:57 Robert Hovhannisyan asked Sep 26, 2019 at 10:52 Robert HovhannisyanRobert Hovhannisyan 3,36166 gold badges2424 silver badges5050 bronze badges 2

• Well where in the recursive function are you actually printing anything to the output? – Bergi Commented Sep 26, 2019 at 10:58
• 1 You should not check whether the object has a .next property, you should check whether nested is null. – Bergi Commented Sep 26, 2019 at 10:59

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4 Answers 4

Sorted by: Reset to default 7

You could return an array with the values and get the nested values after a check

function printList({ value, next }) {
    return [value, ...(next ? printList(next) : [])]
}

let list = { value: 1, next: { value: 2, next: { value: 3, next: { value: 4, next: null } } } };

console.log(printList(list));

You can create a function which checks to see if next is defined for a given object, if it is, you can add the value into an array, along with the rest of the values retrieved from further recursive calls:

const list = {
  value: 1,
  next: {
    value: 2,
    next: {
      value: 3,
      next: {
        value: 4,
        next: null
      }
    }
  }
};

const get_keys = ({value, next}) => 
	next ? [value, ...get_keys(next)] : [value];
  
console.log(get_keys(list));

Here's a method that attempts to stay close to your own attempt.

let list = {
  value: 1,
  next: {
    value: 2,
    next: {
      value: 3,
      next: {
        value: 4,
        next: null
      }
    }
  }
};

function printList(list){
  if (!list)
    return;

  console.log(list.value)

  if (list.hasOwnProperty('next'))
    printList(list.next);
}

printList(list)

var sum = 0;
function printList(list) {
  if (list.next) {
    sum = sum + list.value;
    printList(list.next);
  }
  if (!list.next) {
    sum = sum + list.value;
  }
  return sum;
}
console.log(printList(list));