Intro

Last time, we talked about the theory behind a Singly Linked List.

Today, we start implementing it.

Recap fromlast time

• real life example: a treasure hunt, where you have a starting point and have to seek places and solve riddles in a particular order; the current place knows about the next place, but the current place doesn't know about the previous place
• consists of nodes
• each node has a value and a pointer to the next node (or null at the end of the list)
• has a head (=start), a tail (=end) and a length
• "singly" because only one connection to another node (the next one)

Setup

So we need two basic entities:

• a single place with a riddle (=> anode)
• the complete treasure hunt (=> theSingly Linked List)

Node

• create a file namedsingly-linked-list.js
• add this code

// name of the classclassNode{// the constructor runs when using the class with `new` (see later)constructor(value){// set this nodes value property to the instantiation valuethis.value=value;// set this nodes next property to `null`this.next=null;}}

This is a JavaScript class. Under the hood it uses a function, but it doesn't matter, it's all about the concept. We use this object oriented approach, because it is simple to understand.

We have a class and this class acts as a blueprint for a node.

We can instantiate a new instance of this class and save it into a variable:

constnewNode=newNode("Empire State Building");

The string "Empire State Building" becomes thevalue in the constructor, sothis.value becomes"Empire State Building".this.next becomesnull.

We can see this by logging it:

console.log(newNode);// Node { value: 'Empire State Building', next: null }

We can now create as many nodes as we need by usingnew Node()

Singly Linked List

• add this code tosingly-linked-list.js

// name of the classclassSinglyLinkedList{// the constructor runs when using the class with `new`constructor(){// set this lists length property to `0`this.length=0;// set this lists head property to `null`this.head=null;// set this lists tail property to `null`this.tail=null;}}

Similar to ourNode. Every instance of the Singly Linked List gets alength, ahead and atail.

We can instantiate a new instance of this class and save it into a variable:

constnewSinglyLinkedList=newSinglyLinkedList();

Because all of our three properties are set to default values in the constructor, we don't need arguments.

We can see this by logging it:

console.log(newSinglyLinkedList);// SinglyLinkedList { length: 0, head: null, tail: null }

We can now create our Singly Linked List by usingnew SinglyLinkedList().

Next Part

We will implement how to add a node at the end of the Singly Linked List. If you want to be notified,subscribe :)

Questions

• Did you ever use a Singly Linked List in a project? Why?
• Did you ever use classes in JavaScript?