added CircularLinkedList class in ES6 syntax

Author: loiane

chapter05/05-CircularLinkedList2.js

@@ -0,0 +1,201 @@
+let CircularLinkedList2 = (function () {
+
+    class Node {
+        constructor(element) {
+            this.element = element;
+            this.next = null;
+        }
+    }
+
+    const length = new WeakMap();
+    const head = new WeakMap();
+
+    class CircularLinkedList2 {
+
+        constructor () {
+            length.set(this, 0);
+            head.set(this, null);
+        }
+
+        append(element) {
+
+            let node = new Node(element),
+                current;
+
+            if (this.getHead() === null) { //first node on list
+                head.set(this, node);
+            } else {
+
+                current = this.getHead();
+
+                //loop the list until find last item
+                while (current.next !== this.getHead()) { //last element will be head instead of NULL
+                    current = current.next;
+                }
+
+                //get last item and assign next to added item to make the link
+                current.next = node;
+            }
+
+            //set node.next to head - to have circular list
+            node.next = this.getHead();
+
+            //update size of list
+            let l = this.size();
+            l++;
+            length.set(this, l);
+        }
+
+        insert(position, element) {
+
+            //check for out-of-bounds values
+            if (position >= 0 && position <= this.size()) {
+
+                let node = new Node(element),
+                    current = this.getHead(),
+                    previous,
+                    index = 0;
+
+                if (position === 0) { //add on first position
+
+                    node.next = current;
+
+                    //update last element
+                    while (current.next !== head) { //last element will be head instead of NULL
+                        current = current.next;
+                    }
+
+                    head.set(this, node);
+                    current.next = this.getHead();
+
+                } else {
+                    while (index++ < position) {
+                        previous = current;
+                        current = current.next;
+                    }
+                    node.next = current;
+                    previous.next = node;
+                }
+
+                //update size of list
+                let l = this.size();
+                l++;
+                length.set(this, l);
+
+                return true;
+
+            } else {
+                return false;
+            }
+        }
+
+        removeAt(position) {
+
+            //check for out-of-bounds values
+            if (position > -1 && position < this.size()) {
+
+                let current = this.getHead(),
+                    previous,
+                    index = 0;
+
+                //removing first item
+                if (position === 0) {
+
+                    while (current.next !== head) { //needs to update last element first
+                        current = current.next;
+                    }
+
+                    head.set(this, this.getHead().next);
+                    current.next = this.getHead();
+
+                } else { //no need to update last element for circular list
+
+                    while (index++ < position) {
+
+                        previous = current;
+                        current = current.next;
+                    }
+
+                    //link previous with current's next - skip it to remove
+                    previous.next = current.next;
+                }
+
+                let l = this.size();
+                l--;
+                length.set(this, l);
+
+                return current.element;
+
+            } else {
+                return null;
+            }
+        }
+
+        remove(element) {
+
+            let index = indexOf(element);
+            return removeAt(index);
+        }
+
+        indexOf(element) {
+
+            let current = this.getHead(),
+                index = -1;
+
+            //check first item
+            if (element == current.element) {
+                return 0;
+            }
+
+            index++;
+
+            //check in the middle of the list
+            while (current.next !== this.getHead()) {
+
+                if (element == current.element) {
+                    return index;
+                }
+
+                current = current.next;
+                index++;
+            }
+
+            //check last item
+            if (element == current.element) {
+                return index;
+            }
+
+            return -1;
+        }
+
+        isEmpty() {
+            return this.size() === 0;
+        }
+
+        size() {
+            return length.get(this);
+        }
+
+        getHead() {
+            return head.get(this);
+        }
+
+        toString() {
+
+            let current = this.getHead(),
+                s = current.element;
+
+            while (current.next !== this.getHead()) {
+                current = current.next;
+                s += ', ' + current.element;
+            }
+
+            return s.toString();
+        }
+
+        print() {
+            console.log(this.toString());
+        }
+    }
+    return CircularLinkedList2;
+})();

chapter05/06-UsingCircularLinkedList.html

@@ -5,7 +5,8 @@
     <title></title>
 </head>
 <body>
-<script type="text/javascript" src="05-CircularLinkedList.js"></script>
-<script type="text/javascript" src="06-UsingCircularLinkedList.js"></script>
+<script src="05-CircularLinkedList.js"></script>
+<script src="05-CircularLinkedList2.js"></script>
+<script src="06-UsingCircularLinkedList.js"></script>
 </body>
 </html>

chapter05/06-UsingCircularLinkedList.js

@@ -1,6 +1,6 @@
-let circularLinkedList = new CircularLinkedList();
+let circularLinkedList = new CircularLinkedList2();
 
-circularLinkedList.append(15);
+/*circularLinkedList.append(15);
 circularLinkedList.print();
 
 circularLinkedList.append(16);
@@ -25,4 +25,4 @@ circularLinkedList.removeAt(2);
 circularLinkedList.print();
 
 console.log(circularLinkedList.indexOf(14.5));
-console.log(circularLinkedList.indexOf(16));
+console.log(circularLinkedList.indexOf(16));*/