Add LinkedList.

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

@@ -28,7 +28,35 @@ export default class LinkedList {
   }
 
   prepend(value) {
+    const newNode = new Node(value);
     this.head = new Node(value, this.head);
+
+    return newNode;
+  }
+
+  delete(value) {
+    if (!this.head) {
+      return null;
+    }
+
+    let deletedNode = null;
+
+    if (this.head.value === value) {
+      deletedNode = this.head;
+      this.head = this.head.next;
+    }
+
+    let currentNode = this.head;
+
+    while (currentNode.next) {
+      if (currentNode.next.value === value) {
+        deletedNode = currentNode.next;
+        currentNode.next = currentNode.next.next;
+      }
+      currentNode = currentNode.next;
+    }
+
+    return deletedNode;
   }
 
   toArray() {

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

@@ -3,21 +3,51 @@ import LinkedList from '../LinkedList';
 describe('LinkedList', () => {
   it('should create empty linked list', () => {
     const linkedList = new LinkedList();
-    expect(linkedList).toBeDefined();
+    expect(linkedList.toString()).toBe('');
   });
 
   it('should append node to linked list', () => {
     const linkedList = new LinkedList();
-    linkedList.append(1);
-    linkedList.append(2);
+
+    const node1 = linkedList.append(1);
+    const node2 = linkedList.append(2);
+
+    expect(node1.value).toBe(1);
+    expect(node2.value).toBe(2);
+
     expect(linkedList.toString()).toBe('1,2');
   });
 
   it('should prepend node to linked list', () => {
     const linkedList = new LinkedList();
+
+    const node1 = linkedList.append(1);
+    const node2 = linkedList.prepend(2);
+
+    expect(node1.value).toBe(1);
+    expect(node2.value).toBe(2);
+
+    expect(linkedList.toString()).toBe('2,1');
+  });
+
+  it('should delete node by value from linked list', () => {
+    const linkedList = new LinkedList();
+
     linkedList.append(1);
     linkedList.append(2);
-    linkedList.prepend(3);
-    expect(linkedList.toString()).toBe('3,1,2');
+    linkedList.append(3);
+    linkedList.append(3);
+    linkedList.append(4);
+    linkedList.append(5);
+
+    const deletedNode = linkedList.delete(3);
+    expect(deletedNode.value).toBe(3);
+    expect(linkedList.toString()).toBe('1,2,3,4,5');
+
+    linkedList.delete(3);
+    expect(linkedList.toString()).toBe('1,2,4,5');
+
+    linkedList.delete(1);
+    expect(linkedList.toString()).toBe('2,4,5');
   });
 });