## Intro

Last time, we learned how to pop a new node from the end of our Singly Linked List.

Today, we learn how to unshift something to the list. `Unshift`

means `add something to the beginning`

.

## Current Code

We start with the code from the setup, without `push`

and `pop`

, because we want to keep the code as simple as possible to understand.

```
class Node {
constructor(value) {
this.value = value;
this.next = null;
}
}
class SinglyLinkedList {
constructor() {
this.length = 0;
this.head = null;
this.tail = null;
}
}
```

## Thoughts

First, we should think about the constraints and possibilities:

If there is currently NO other node in the Singly Linked List (so it is currently empty):

- create a new node
- set the new node as the Singly Linked List's
`tail`

- set the new node as the Singly Linked List's
`head`

- increase the Singly Linked List's length by 1
- return the new node

If there is at least 1 node in the Singly Linked List:

- create a new node
- set the new node's
`next`

to the Singly Linked List's current`head`

- set the new node as the Singly Linked List's
`head`

- increase the Singly Linked List's length by 1
- return the new node

Examples:

- 0 nodes: before: null (head & tail) => after: A (head & tail)
- 1 node: before: A (head & tail) => after: A-1 (head) -> A (tail)
- n nodes: before: A (head) -> ... -> n (tail) => after: A-1 (head) -> A -> ... -> n (tail)

Differences:

- there is only one difference: the step after creating a new node

## Implementation (Short version, DRY)

```
class Node {
constructor(value) {
this.value = value;
this.next = null;
}
}
class SinglyLinkedList {
constructor() {
this.length = 0;
this.head = null;
this.tail = null;
}
unshift(value) {
// create a new node
const newNode = new Node(value);
// check if Singly Linked List is empty
if (!this.length) {
// set the new node as the Singly Linked List's `tail`
this.tail = newNode;
} else {
// set the new node's `next` to the Singly Linked List's current `head`
newNode.next = this.head;
}
// set the new node as the Singly Linked List's `head`
this.head = newNode;
// increase the Singly Linked List's length by 1
this.length += 1;
// return the new node
return newNode;
}
}
```

## Result

Let's have a look how to use the Singly Linked List `unshift`

method and its results.

```
const newSLL = new SinglyLinkedList();
// should be empty
console.log(newSLL);
// SinglyLinkedList { length: 0, head: null, tail: null }
console.log(newSLL.unshift("1"));
// Node { value: '1', next: null }
// should be a list with the new node with value 1
console.log(newSLL);
/*
* SinglyLinkedList {
* length: 1,
* head: Node { value: '1', next: null },
* tail: Node { value: '1', next: null }
* }
*/
console.log(newSLL.unshift("2"));
// Node { value: '2', next: Node { value: '1', next: null } }
// should be a list with the new node with value 2 and 1 (from the last unshift)
console.log(newSLL);
/*
* SinglyLinkedList {
* length: 2,
* head: Node { value: '2', next: Node { value: '1', next: null } },
* tail: Node { value: '1', next: null }
* }
*/
```

### Next Part

We will implement how to remove a node from the beginning of the Singly Linked List. If you want to be notified, subscribe :)