# Javascript Program For Writing A Function To Get Nth Node In A Linked List

Write a GetNth() function that takes a linked list and an integer index and returns the data value stored in the node at that index position.

Example:

`Input:  1 -> 10 -> 30 -> 14,  index = 2Output: 30  Explanation: The node at index 2 is 30`

## Method 1 – Using Loop

Algorithm:

`1. Initialize count = 02. Loop through the link list     a. If count is equal to the passed index then return current node     b. Increment count     c. change current to point to next of the current.`

Implementation:

## Javascript

 `// Javascript program to find nth  ` `// node of a linked list ` ` `  `class Node { ` `    ``constructor(d) { ` `        ``this``.data = d; ` `        ``this``.next = ``null``; ` `    ``} ` `} ` ` `  `// Head of list ` `let head; ` ` `  `/* Takes index as argument and  ` `   ``return data at index */` `function` `GetNth(index) { ` `    ``let current = head; ` ` `  `    ``// Index of Node we are currently  ` `    ``// looking at ` `    ``let count = 0; ` ` `  `    ``while` `(current != ``null``) { ` `        ``if` `(count == index) ` `            ``return` `current.data; ` `        ``count++; ` `        ``current = current.next; ` `    ``} ` ` `  `    ``/* if we get to this line, the caller  ` `       ``was asking for a non-existent element  ` `       ``so we assert fail */` `    ``assert(``false``); ` `    ``return` `0; ` `} ` ` `  `/* Given a reference to the head of a  ` `   ``list and an int, inserts a new Node  ` `   ``on the front of the list */` `function` `push(new_data) { ` ` `  `    ``// 1. Create new Node and put data  ` `    ``let new_Node = ``new` `Node(new_data); ` ` `  `    ``// 2. Make next of new Node as head ` `    ``new_Node.next = head; ` ` `  `    ``// 3. Move the head to point to new Node ` `    ``head = new_Node; ` `} ` ` `  `// Driver code ` ` `  `// Start with empty list  ` `// Use push() method to construct list  ` `// 1 -> 12 -> 1 -> 4 -> 1 ` `push(1); ` `push(4); ` `push(1); ` `push(12); ` `push(1); ` ` `  `// Check the count function  ` `console.log(``"Element at index 3 is "` `+ ` `    ``GetNth(3));`

Output

```Element at index 3 is 4
```

Time Complexity: O(n)

Space Complexity: O(1) since using constant space to create nodes and variables.

## Method 2 – Using Recursion

Algorithm:

`getnth(node,n)1. Initialize count = 02. if count==n     return node->data3. else    return getnth(node->next, n-1)`

Implementation:

## Javascript

 `// JavaScript program to find n'th node  ` `// of a linked list using recursion     ` ` `  `// Linked List node ` `class Node { ` `    ``constructor(val) { ` `        ``this``.data = val; ` `        ``this``.next = ``null``; ` `    ``} ` `} ` ` `  `/* Given a reference (pointer to pointer) to the ` `   ``head of a list and an int, push a new node on ` `   ``the front of the list. */` `function` `push(head, new_data) { ` `     `  `    ``// Allocate node ` `    ``let new_node = ``new` `Node(new_data); ` ` `  `    ``// Put in the data  ` `    ``new_node.data = new_data; ` ` `  `    ``new_node.next = head; ` `    ``head = new_node; ` `    ``return` `head; ` `} ` ` `  `/* Takes head pointer of the linked list and  ` `   ``index as arguments and return data at index */` `function` `GetNth(head, n) { ` `    ``let count = 0; ` ` `  `    ``// Edge case - if head is null ` `    ``if` `(head == ``null``) ` `        ``return` `-1; ` ` `  `    ``// if count equal too n return node.data ` `    ``if` `(count == n) ` `        ``return` `head.data; ` ` `  `    ``// Recursively decrease n and increase ` `    ``// head to next pointer ` `    ``return` `GetNth(head.next, n - 1); ` `} ` ` `  `// Driver code ` ` `  `// Start with the empty list  ` `let head = ``null``; ` ` `  `// Use push() to construct list ` `// 1 -> 12 -> 1 -> 4 -> 1 ` `head = push(head, 1); ` `head = push(head, 4); ` `head = push(head, 1); ` `head = push(head, 12); ` `head = push(head, 1); ` ` `  `// Check the count function  ` `console.log(``"Element at index 3 is "``, ` `    ``GetNth(head, 3));`

Output

```Element at index 3 is  4
```

Time Complexity: O(n)

Space Complexity: O(n) for call stack because using recursion

Please refer complete article on Write a function to get Nth node in a Linked List for more details!

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