Minor code style fixes for DoublyLinkedList.

Author: trekhleb

src/data-structures/doubly-linked-list/DoublyLinkedList.js

@@ -78,38 +78,44 @@ export default class DoublyLinkedList{
 letdeletedNode=null;
 letcurrentNode=this.head;
 
-do{
+while(currentNode){
 if(this.compare.equal(currentNode.value,value)){
 deletedNode=currentNode;
 
 if(deletedNode===this.head){
+// If HEAD is going to be deleted...
+
 // Set head to second node, which will become new head.
 this.head=deletedNode.next;
 
-// Set new head's previous to null
+// Set new head's previous to null.
 if(this.head){
 this.head.previous=null;
 }
 
 // If all the nodes in list has same value that is passed as argument
-// then all nodes will get deleted, therefore tail needs to be updated
+// then all nodes will get deleted, therefore tail needs to be updated.
 if(deletedNode===this.tail){
 this.tail=null;
 }
 }elseif(deletedNode===this.tail){
-// set tail to second last node, which will become new tail
+// If TAIL is going to be deleted...
+
+// Set tail to second last node, which will become new tail.
 this.tail=deletedNode.previous;
 this.tail.next=null;
 }else{
+// If MIDDLE node is going to be deleted...
 constpreviousNode=deletedNode.previous;
 constnextNode=deletedNode.next;
+
 previousNode.next=nextNode;
 nextNode.previous=previousNode;
 }
 }
 
 currentNode=currentNode.next;
-}while(currentNode);
+}
 
 returndeletedNode;
 }
@@ -149,16 +155,22 @@ export default class DoublyLinkedList{
  */
 deleteTail(){
 if(!this.tail){
+// No tail to delete.
 returnnull;
-}elseif(this.head===this.tail){
+}
+
+if(this.head===this.tail){
+// There is only one node in linked list.
 constdeletedTail=this.tail;
 this.head=null;
 this.tail=null;
 
 returndeletedTail;
 }
 
+// If there are many nodes in linked list...
 constdeletedTail=this.tail;
+
 this.tail=this.tail.previous;
 this.tail.next=null;
 

src/data-structures/linked-list/LinkedList.js

@@ -128,13 +128,15 @@ export default class LinkedList{
  */
 deleteTail(){
 if(this.head===this.tail){
+// There is only one node in linked list.
 constdeletedTail=this.tail;
 this.head=null;
 this.tail=null;
 
 returndeletedTail;
 }
 
+// If there are many nodes in linked list...
 constdeletedTail=this.tail;
 
 // Rewind to the last node and delete "next" link for the node before the last one.
@@ -148,6 +150,7 @@ export default class LinkedList{
 }
 
 this.tail=currentNode;
+
 returndeletedTail;
 }