linked lists

<script>

// A complete working javascript program
// to demonstrate all insertion methods
// on linked list
	var head; // head of list

	/* Linked list Node */
	class Node {
			constructor(val) {
				this.data = val;
				this.next = null;
			}
		}

	/* Inserts a new Node at front of the list. */
	function push(new_data) {
		/*
		* 1 & 2: Allocate the Node & Put in the data
		*/
		var new_node = new Node(new_data);

		/* 3. Make next of new Node as head */
		new_node.next = head;

		/* 4. Move the head to point to new Node */
		head = new_node;
	}

	/* Inserts a new node after the given prev_node. */
	function insertAfter(prev_node , new_data) {
		/* 1. Check if the given Node is null */
		if (prev_node == null) {
			document.write(
			"The given previous node cannot be null"
			);
			return;
		}

		/*
		* 2 & 3: Allocate the Node & Put in the data
		*/
		var new_node = new Node(new_data);

		/* 4. Make next of new Node as next of prev_node */
		new_node.next = prev_node.next;

		/* 5. make next of prev_node as new_node */
		prev_node.next = new_node;
	}

	/*
	* Appends a new node at the end.
	This method is defined inside LinkedList class
	* shown above
	*/
	function append(new_data) {
		/*
		* 1. Allocate the Node & 2.
		Put in the data 3. Set next as null
		*/
		var new_node = new Node(new_data);

		/*
		* 4. If the Linked List is empty,
		then make the new node as head
		*/
		if (head == null) {
			head = new Node(new_data);
			return;
		}

		/*
		* 4. This new node is going to be the last node,
		so make next of it as null
		*/
		new_node.next = null;

		/* 5. Else traverse till the last node */
		var last = head;
		while (last.next != null)
			last = last.next;

		/* 6. Change the next of last node */
		last.next = new_node;
		return;
	}

	/*
	* This function prints contents of linked list
	starting from the given node
	*/
	function printList() {
var tnode = head;
		while (tnode != null) {
			document.write(tnode.data + " ");
			tnode = tnode.next;
		}
	}

	/*
	* Driver program to test above functions.
	Ideally this function should be in a
	* separate user class. It is kept here
	to keep code compact
	*/
	
		/* Start with the empty list */

		// Insert 6. So linked list becomes 6->NUllist
		append(6);

		// Insert 7 at the beginning. So linked list becomes
		// 7->6->NUllist
		push(7);

		// Insert 1 at the beginning. So linked list becomes
		// 1->7->6->NUllist
		push(1);

		// Insert 4 at the end. So linked list becomes
		// 1->7->6->4->NUllist
		append(4);

		// Insert 8, after 7. So linked list becomes
		// 1->7->8->6->4->NUllist
		insertAfter(head.next, 8);

		document.write("\nCreated Linked list is: ");
		printList();

// This code contributed by gauravrajput1

</script>