feat(stack) is empty

Author: amejiarosario

lib/data-structures/stacks/stack.js

@@ -32,6 +32,13 @@ class Stack {
   get size() {
     return this.input.size;
   }
+
+  /**
+   * Return true if is empty false otherwise true
+   */
+  isEmpty() {
+    return !this.input.size;
+  }
 }
 
 // aliases

lib/data-structures/stacks/stack.spec.js

@@ -27,4 +27,17 @@ describe('Stack', function () {
       expect(stack.pop()).toEqual(undefined);
     });
   });
+
+  describe('#isEmpty', () => {
+    it('should return true when empty', () => {
+      // expect(stack.size).toBe(0);
+      expect(stack.isEmpty()).toBe(true);
+    });
+
+    it('should return false when not empty', () => {
+      stack.add('a');
+      // expect(stack.size).toBe(1);
+      expect(stack.isEmpty()).toBe(false);
+    });
+  });
 });