Assignment 4 Completed

Creating a doubly linked list

by Ron Eaglin

HTML

<fieldset>
  <legend>Assignment 4: Landon Simmons COP3530</legend>
  <table>
    <tr>
      <td>
        Doubly Linked List
        <input type='textbox' id='nodeValue' value='100' />
      </td>
      <td>
        <button id='button' onclick="addNode();" value="2">
          Send number
        </button>
      </td>
    </tr>
  </table>
</fieldset>
<table>
  <tr>
    <div id='output'></div>
  </tr>
</table>

JavaScript

function LinkedList() {
	this.head = null;
  this.tail = null;
  this.length = 0;
}

function Node() {
	this.next = null;
  this.prev = null;
  this.content = null;
  this.id = null;
}




//_ represents anything that is being passed to the function
LinkedList.prototype.add = function(_content, _id) {
	
  //
  var node = new Node(); node.content = _content; node.id = _id;
  
  //setting the value for the head of the node - this is setup for the first node only
  if (this.head == null) {
  	this.head = node; this.length = 1;
    return node;
  }
  
  //this is to set the value for the tail of the node
  if (this.tail == null) {
  	//new node that was created is setting the pointer of the tail to itself
    this.tail = node;
    //the tail of the past node is now being referenced in the head of the current node 
    this.tail.prev = this.head;
    //the current tail is attached the next method so the next node if it's added can reference it
    this.head.next = this.tail;
    //increasing the length ??
    this.length = 2;
    //this.id = 2;
    return node;
  }
  //This the setup for the 3rd the node is setup 
  this.tail.next = node;
  node.prev = this.tail;
  this.tail = node;
  this.length++;
  return node;
  
}





LinkedList.prototype.print = function() {
	if (this.head == null) return "Empty List";
  var s = "";
  var node = this.head;
  while (node != null) {
  	s += "Content: " + node.content + "<emsp> " + " id: " + node.id +"</br>";
    node = node.next;
  }
  return s;
}

//calling a new object to use the linkedlist class constructor
var aList = new LinkedList();
//global counter for the nodes
var id = 0;
//creating the nodes before the user can add anything
createNode();

function addNode() {
  var c = document.getElementById("nodeValue").value;
	//debugger;
  //passing the users value to the content portion of the node 
  aList.add(c, id = ++id);
  //calling the print function to pull the content from the nodes*
 ...