Added queue functionality and unit test cases

Author: linux-nerd

karma.conf.js

@@ -34,7 +34,6 @@ module.exports = function (config) {
     // preprocess matching files before serving them to the browser
     // available preprocessors: https://npmjs.org/browse/keyword/karma-preprocessor
     preprocessors: {
-      'src/test-index.spec.js': ['webpack'],
       'src/**/*.js': ['webpack', 'coverage']
     },
 

lib/data-structures.js

@@ -0,0 +1,36 @@
+const _queue = Symbol('queue');
+
+export class Queue {
+  constructor() {
+    this[_queue] = [];
+  }
+  get queue() {
+    return this[_queue];
+  }
+  enqueue(o) {
+    this[_queue].unshift(o);
+  }
+  dequeue() {
+    if (this.isEmpty()) {
+      return new Error('The Queue is Empty');
+    } else {
+      this[_queue].pop();
+    }
+  }
+
+  size() {
+    return this[_queue].length;
+  }
+
+  isEmpty() {
+    return this.size() === 0;
+  }
+
+  top() {
+    return !this.isEmpty() ? this[_queue][this.size() - 1] : new Error('The Queue is Empty');
+  }
+
+  clear() {
+    this[_queue].length = 0;
+  }
+}

lib/data-structures.js.map

@@ -0,0 +1,78 @@
+import { Queue } from './queue';
+
+describe('Queue', () => {
+  let q;
+  beforeEach(() => {
+    q = new Queue;
+  });
+
+  it('should create a new queue', () => {
+    expect(q).toBeDefined();
+    expect(q.size()).toBe(0);
+    expect(q.isEmpty()).toBeTruthy();
+    expect(q.queue).toEqual([]);
+  });
+
+  it('should insert values in the queue', () => {
+    q.enqueue('a');
+    expect(q.size()).toBe(1);
+    expect(q.isEmpty()).toBeFalsy();
+    expect(q.queue).toEqual(['a']);
+
+    q.enqueue('b');
+    expect(q.size()).toBe(2);
+    expect(q.isEmpty()).toBeFalsy();
+    expect(q.queue).toEqual(['b', 'a']);
+  });
+
+  describe('Dequeue, Top and Clear functionality', () => {
+    beforeEach(() => {
+      q.enqueue('a');
+      q.enqueue('b');
+      q.enqueue('c');
+    });
+
+    it('should dequeue value', () => {
+      expect(q.size()).toBe(3);
+      expect(q.queue).toEqual(['c', 'b', 'a']);
+
+      q.dequeue();
+      expect(q.size()).toBe(2);
+      expect(q.queue).toEqual(['c', 'b']);
+
+      q.dequeue();
+      expect(q.size()).toBe(1);
+      expect(q.queue).toEqual(['c']);
+
+      q.dequeue();
+      expect(q.size()).toBe(0);
+      expect(q.queue).toEqual([]);
+
+      expect(q.dequeue().message).toBe('The Queue is Empty')
+    });
+
+    it('should remove all elements from the queue', () => {
+      expect(q.size()).toBe(3);
+      expect(q.queue).toEqual(['c', 'b', 'a']);
+
+      q.clear();
+      expect(q.size()).toBe(0);
+      expect(q.queue).toEqual([]);
+    });
+
+    it('should return top element from the queue', () => {
+      expect(q.size()).toBe(3);
+      expect(q.queue).toEqual(['c', 'b', 'a']);
+      expect(q.top()).toBe('a');
+    });
+
+    it('should return error message The Queue is Empty when top is fetched from an empty queue', () => {
+      expect(q.size()).toBe(3);
+
+      q.clear();
+      expect(q.size()).toBe(0);
+
+      expect(q.top().message).toBe('The Queue is Empty');
+    });
+  });
+});

src/queue/queue.js

@@ -1,3 +1,4 @@
 require('./binary-search-tree/binary-search-tree.spec');
 require('./graph/graph.spec');
-require('./graph/adj-list.spec');
+require('./queue/queue.spec');
+require('./graph/adj-list.spec');