fix error in SinglyLinkedList head method (TheAlgorithms#1322)

BekzodIsakov · web-flow · commit 1666c3a0be27 · 2023-05-15T13:35:09.000+05:30
* fix error in SinglyLinkedList head method

* test: update check head test for SinglyLinkedList

* fix: code style error

* fix: remove extra semicolons

---------

Co-authored-by: Bekzod &lt;bekzodisakov18@gmail.com&gt;
diff --git a/Data-Structures/Linked-List/SinglyLinkedList.js b/Data-Structures/Linked-List/SinglyLinkedList.js
@@ -40,12 +40,12 @@ class LinkedList {
 
   // Returns the head
   head () {
-    return this.headNode?.data || null
+    return this.headNode?.data ?? null
   }
 
   // Returns the tail
   tail () {
-    return this.tailNode?.data || null
+    return this.tailNode?.data ?? null
   }
 
   // Return if the list is empty
diff --git a/Data-Structures/Linked-List/test/SinglyLinkedList.test.js b/Data-Structures/Linked-List/test/SinglyLinkedList.test.js
@@ -148,6 +148,10 @@ describe('SinglyLinkedList', () => {
 
     list.addFirst(30)
     expect(list.head()).toBe(30)
+
+    // check for a falsy head data
+    list.addFirst(false)
+    expect(list.head()).toBe(false)
   })
 
   it('Check tail', () => {
@@ -162,6 +166,10 @@ describe('SinglyLinkedList', () => {
 
     list.addFirst(30)
     expect(list.tail()).toBe(20)
+
+    // check for a falsy tail data
+    list.addLast(false)
+    expect(list.tail()).toBe(false)
   })
 
   it('Check size', () => {

Original file line number	Diff line number	Diff line change
`@@ -40,12 +40,12 @@ class LinkedList {`
`40`	`40`
`41`	`41`	`// Returns the head`
`42`	`42`	`head () {`
`43`		`- return this.headNode?.data \|\| null`
	`43`	`+ return this.headNode?.data ?? null`
`44`	`44`	`}`
`45`	`45`
`46`	`46`	`// Returns the tail`
`47`	`47`	`tail () {`
`48`		`- return this.tailNode?.data \|\| null`
	`48`	`+ return this.tailNode?.data ?? null`
`49`	`49`	`}`
`50`	`50`
`51`	`51`	`// Return if the list is empty`