update: re-implementation of Queue, fix in tests

Author: ashokdey

src/_DataStructures_/Queue/Queue.test.js

@@ -69,14 +69,5 @@ describe('Data Structure : Queue', () => {
       queue.destroy();
       expect(queue.length()).toEqual(0);
     });
-
-    it('Override and throw error for other LL methods', () => {
-      expect(() => { queue.addAtBeginning(); }).toThrowError('Not Allowed');
-      expect(() => { queue.addAt(); }).toThrowError('Not Allowed');
-      expect(() => { queue.removeFromEnd(); }).toThrowError('Not Allowed');
-      expect(() => { queue.getLast(); }).toThrowError('Not Allowed');
-      expect(() => { queue.getAt(); }).toThrowError('Not Allowed');
-      expect(() => { queue.removeAt(); }).toThrowError('Not Allowed');
-    });
   });
 });

src/_DataStructures_/Queue/index.js

@@ -1,56 +1,54 @@
-const { LinkedList: SinglyLinkedLists } = require('../LinkedList');
+const { LinkedList: SLL } = require('../LinkedList');
 
-class Queue extends SinglyLinkedLists {
+class Queue {
   constructor() {
-    super();
-    this.NotAllowed = 'Not Allowed';
+    this.data = this.getStorage();
   }
 
-  enqueue(data) {
-    return this.addAtEnd(data);
+  enqueue(element) {
+    this.data.enqueue(element);
   }
 
   dequeue() {
-    const node = this.removeFromBeginning();
-    return node ? node.data : node;
+    return this.data.dequeue();
   }
 
   peek() {
-    const node = this.getFirst();
-    return node ? node.data : node;
+    return this.data.peek();
   }
 
   length() {
-    return this.size;
+    return this.data.length();
   }
 
   destroy() {
-    this.delete();
-  }
-
-  /** Override and throw error for other LL methods */
-  addAtBeginning() {
-    throw new Error(this.NotAllowed);
-  }
-
-  addAt() {
-    throw new Error(this.NotAllowed);
-  }
-
-  removeFromEnd() {
-    throw new Error(this.NotAllowed);
-  }
-
-  getLast() {
-    throw new Error(this.NotAllowed);
-  }
-
-  getAt() {
-    throw new Error(this.NotAllowed);
-  }
-
-  removeAt() {
-    throw new Error(this.NotAllowed);
+    return this.data.destroy();
+  }
+
+  // eslint-disable-next-line class-methods-use-this
+  getStorage() {
+    // encapsulating the internal implementation here
+    const storage = new SLL();
+
+    return {
+      enqueue(element) {
+        return storage.addAtEnd(element);
+      },
+      dequeue() {
+        const node = storage.removeFromBeginning();
+        return node ? node.data : node;
+      },
+      peek() {
+        const node = storage.getFirst();
+        return node ? node.data : node;
+      },
+      length() {
+        return storage.size;
+      },
+      destroy() {
+        storage.delete();
+      },
+    };
   }
 }