link_list.js

// class Node {
//   constructor(value) {
//     this.value = value;
//     this.next = null;
//   }
// }

// const head = new Node(29);
// head.next = new Node(30);
// head.next.next = new Node(31);

// let temp = head;

// while (temp !== null) {
//   console.log(temp.value, " ");
//   temp = temp.next;
// }
// console.log(head);

// ! link list part 2

class Node {
  constructor(value) {
    this.value = value;
    this.next = null;
  }
}

class Link_List {
  constructor() {
    this.head = null;
    this.tail = null;
    this.length = null;
  }
  //? start  append logic
  append(value) {
    //if the link list is empty
    const newNode = new Node(value);
    if (this.head === null) {
      this.head = newNode;
      this.tail = newNode;
    } else {
      //  if the link list in not empty ?
      this.tail.next = newNode;
      this.tail = newNode;
    }
    this.length++;
  }

  // ? start prepend logic
  prepend(value) {
    const newNode = new Node(value);

    if (this.head === null) {
      this.head = newNode;
      this.tail = newNode;
    } else {
      //  if the link list in not empty ?
      newNode.next = this.head;
      this.head = newNode;
    }
  }

  // ? start  insert logic
  insert(index, value) {
    // check input index is less then this.length
    if (index < 0 || index > this.length) {
      console.error("index out of bound :");
      return undefined;
    }

    // * if the insert is in the start of the linked list

    if (index === 0) {
      return this.prepend(value);
    }

    // * in the insert is in the end of the linked list
    if (index === this.length) {
      return this.append(value);
    }

    //* if the insert is in the middle or the linked list
    //? find the leading node

    const leadingNode = this._traverseToIndex(index - 1);

    const holdingNode = leadingNode.next;
    const newNode = new Node(value);

    leadingNode.nex = newNode;
    newNode.next = holdingNode;

    this.length++;
  }

  //* reusable function insert and remove / privet helper method
  _traverseToIndex(index) {
    let count = 0;
    let currentNode = this.head;

    while (count !== index) {
      currentNode = currentNode.next;
      count++;
    }

    return currentNode;
  }
  // ? start remove logic
  remove() {}

  //?  start print
  print() {
    let currentNode = this.head;

    while (currentNode !== null) {
      console.log("currentNode :", currentNode.value);
      currentNode = currentNode.next;
    }
  }
}

const linkList = new Link_List();
// link list append check
linkList.append(0);
linkList.append(1);
linkList.append(3);

linkList.insert(2, 200);

//* link list prepend check
// linkList.prepend(20);
// linkList.prepend(30);
// linkList.prepend(40);

// insert the index and value in link list
// linkList.insert(2, 199);

linkList.print();