Refactor

src/World.ts

@@ -1,9 +1,4 @@
-import {
-  addVectors,
-  createMultiple,
-  divideVectors,
-  Vector2,
-} from "./helperFunctions";
+import { calculateCenter, createMultiple, Vector2 } from "./helperFunctions";
 import {
   heroFactory,
   zombieFactory,
@@ -107,16 +102,11 @@ export class World {
     return this.entities.get(entityKey)?.[index];
   }
 
-  centerOfEntityScreenPosition(entity: Entity): Vector2 {
-    const middleOfEntity = divideVectors(entity.widthHeight, [2, 2]);
-    return addVectors(entity.position, middleOfEntity);
-  }
-
   addBullet(): void {
     const hero = this.entities.get("hero"); // get possible undefined?
     this.entities.get("bullets")?.push(
       bulletFactory({
-        position: this.centerOfEntityScreenPosition(hero?.[0]),
+        position: calculateCenter(hero?.[0]),
         rotation: hero?.[0].rotation,
       })
     );

src/helperFunctions.ts

@@ -1,3 +1,5 @@
+import type { Entity } from "./World";
+
 export type Vector2 = [number, number];
 
 export const createMultiple = <T>(
@@ -6,8 +8,14 @@ export const createMultiple = <T>(
 ): T[] => Array.from({ length: numberOfClasses }, factory);
 
 type VectorFn = (x: Readonly<Vector2>, y: Readonly<Vector2>) => Vector2;
+
 export const addVectors: VectorFn = (x, y) => [x[0] + y[0], x[1] + y[1]];
+
 export const divideVectors: VectorFn = (x, y) => [x[0] / y[0], x[1] / y[1]];
+
+export const calculateCenter = (entity: Readonly<Entity>): Vector2 =>
+  addVectors(entity.position, divideVectors(entity.widthHeight, [2, 2]));
+
 export const calculateRandomPositionAroundPoint: VectorFn = (
   centrePoint,
   screenWidthHeight