fixed typing and tests in strict mode

Author: sharunkumar

src/index.ts

@@ -31,7 +31,7 @@ import { IPriorityQueue } from '../typings/priority-queue';
  */
 export class PriorityQueue<T> implements IPriorityQueue<T> {
   private _queue: T[];
-  private _comparator: (item1: T, item2: T) => boolean;
+  private _comparator?: (item1: T, item2: T) => boolean;
 
   constructor(comparator?: (item1: T, item2: T) => boolean) {
     this._queue = [];

test/priority-queue.spec.ts

@@ -16,7 +16,7 @@ describe('testing priority queue', () => {
     });
 
     afterEach(() => {
-      p = null;
+      p = new PriorityQueue();
     });
 
     it('should return max heap of test case 1', () => {
@@ -193,7 +193,7 @@ describe('testing priority queue', () => {
     });
 
     afterEach(() => {
-      p = null;
+      p = new PriorityQueue();
     });
 
     it('should return min heap of test case 1', () => {
@@ -233,7 +233,7 @@ describe('testing priority queue', () => {
     });
 
     afterEach(() => {
-      p = null;
+      p = new PriorityQueue();
     });
 
     it('should return true - with array of numbers', () => {

tsconfig.json

@@ -5,12 +5,12 @@
   "compilerOptions": {
     "outDir": "./dist",
     "noImplicitAny": false,
-    "noImplicitUseStrict": true,
     "module": "CommonJS",
     "target": "ESNext",
     "allowJs": true,
     "moduleResolution": "node",
     "esModuleInterop": true,
+    "strict": true,
     "lib": [
       "ES2015",
       "DOM"

typings/priority-queue.d.ts

@@ -10,12 +10,12 @@ export interface IPriorityQueue<T> {
   /**
    * Retrieves, but does not remove, the head of this queue, or returns null if this queue is empty.
    */
-  top: () => T;
+  top: () => T | null;
   /**
    * Retrieves and removes the head of this queue, or returns null if this queue is empty.
    * Everytime pop element from queue, the queue is started "sift down" to rebuild the heap
    */
-  pop: () => T;
+  pop: () => T | null;
   /**
    * Returns the number of elements in this collection.
    */