feature: handled removing an element from an empty queue

hbarcelos · hbarcelos · commit f4f8c9a1e7b0 · 2020-02-05T14:16:10.000-03:00
diff --git a/round-linked-queue.js b/round-linked-queue.js
@@ -30,7 +30,7 @@ class RoundLinkedQueue {
       next: null,
     };
 
-    let removedElement;
+    let removedNode = {};
 
     if (this.length < this.maxLength) {
       if (!this._first) {
@@ -40,23 +40,26 @@ class RoundLinkedQueue {
 
       this._length += 1;
     } else {
-      removedElement = this._first.data;
+      removedNode = this._first;
       this._first = this._first.next;
     }
 
     this._last.next = node;
     this._last = node;
 
-    return removedElement;
+    return removedNode.data;
   }
 
   remove() {
-    const removedElement = this.first;
+    const removedNode = this._first;
+    if (!removedNode) {
+      throw new Error("Cannot remove element from an empty queue");
+    }
 
     this._first = this._first.next;
     this._length -= 1;
 
-    return removedElement;
+    return removedNode.data;
   }
 }
 
diff --git a/round-linked-queue.test.js b/round-linked-queue.test.js
@@ -108,5 +108,11 @@ describe("Round-Queue", () => {
       expect(queue.first).to.equal(2, "should shift the second element to the head of the queue");
       expect(queue.last).to.equal(3, "should not change the last element");
     });
+
+    it("Should throw an error when the queue is empty", () => {
+      const queue = new RoundQueue(3);
+
+      expect(() => queue.remove()).to.throw("Cannot remove element from an empty queue");
+    });
   });
 });
