feat: add size property (#10)

closes #1

README.md

@@ -45,6 +45,12 @@ map.get('key');
 
 ## API
 
+#### size: number
+
+Returns the number of values in the `WeakFlyweightSet` object.
+
+> :warning: Number of values is not precise due to nature of `FinalizationRegistry` object.
+
 #### set(any, object): this
 
 The `set()` method adds or updates an element with a specified key and an object to a `WeakIdentityMap` object.

src/weak-identity-map.ts

@@ -1,13 +1,16 @@
 export class WeakIdentityMap<K, V extends object> {
+  #size: number;
   #map: Map<K, WeakRef<V>>;
   #registry: FinalizationRegistry<{ key: K; ref: WeakRef<V> }>;
 
   constructor() {
+    this.#size = 0;
     this.#map = new Map();
     this.#registry = new FinalizationRegistry((heldValue) => {
       const ref = this.#map.get(heldValue.key);
 
       if (ref === heldValue.ref) {
+        this.#size--;
         this.#map.delete(heldValue.key);
       }
     });
@@ -25,11 +28,13 @@ export class WeakIdentityMap<K, V extends object> {
     const oldValue = this.#map.get(key)?.deref();
 
     if (typeof oldValue !== 'undefined') {
+      this.#size--;
       this.#registry.unregister(oldValue);
     }
 
     const ref = new WeakRef<V>(value);
 
+    this.#size++;
     this.#map.set(key, ref);
     this.#registry.register(value, { key, ref });
 
@@ -40,6 +45,7 @@ export class WeakIdentityMap<K, V extends object> {
     const value = this.#map.get(key)?.deref();
 
     if (typeof value !== 'undefined') {
+      this.#size--;
       this.#registry.unregister(value);
     }
 
@@ -59,6 +65,7 @@ export class WeakIdentityMap<K, V extends object> {
       }
     }
 
+    this.#size = 0;
     this.#map.clear();
   }
 
@@ -132,4 +139,8 @@ export class WeakIdentityMap<K, V extends object> {
       next,
     };
   }
+
+  get size() {
+    return this.#size;
+  }
 }

test/weak-identity-map.test.ts

@@ -15,6 +15,7 @@ describe('WeakIdentityMap', () => {
     map.set(1, entity);
 
     expect(map.has(1)).toBeTruthy();
+    expect(map.size).toBe(1);
     expect(typeof map.get(1) === 'object' && map.get(1) !== null).toBeTruthy();
     expect(map.get(1)).toBe(entity);
   });
@@ -25,6 +26,7 @@ describe('WeakIdentityMap', () => {
     map.set(1, entity);
     map.set(2, entity);
 
+    expect(map.size).toBe(2);
     expect(map.has(1)).toBeTruthy();
     expect(map.has(2)).toBeTruthy();
     expect(Array.from(map.values()).length).toBe(2);
@@ -35,6 +37,9 @@ describe('WeakIdentityMap', () => {
       gc();
 
       try {
+        // TODO: figure out how to force calling FinalizationRegistry callback without mocking it
+        // expect(map.size).toBe(0);
+
         expect(map.has(1)).toBeFalsy();
         expect(map.has(2)).toBeFalsy();
 
@@ -60,6 +65,7 @@ describe('WeakIdentityMap', () => {
       gc();
 
       try {
+        expect(map.size).toBe(1);
         expect(map.has(1)).toBeTruthy();
         expect(map.get(1)).toBe(entity);
 
@@ -76,6 +82,7 @@ describe('WeakIdentityMap', () => {
 
     expect(map.has(1)).toBeTruthy();
     expect(map.delete(1)).toBeTruthy();
+    expect(map.size).toBe(0);
     expect(map.has(1)).toBeFalsy();
   });
 
@@ -90,6 +97,7 @@ describe('WeakIdentityMap', () => {
 
     map.clear();
 
+    expect(map.size).toBe(0);
     expect(map.has(1)).toBeFalsy();
     expect(map.has(2)).toBeFalsy();
   });
@@ -100,6 +108,7 @@ describe('WeakIdentityMap', () => {
     map.set(1, entity);
     map.set(2, entity);
 
+    expect(map.size).toBe(2);
     expect(Array.from(map.keys()).sort()).toEqual([1, 2].sort());
   });
 
@@ -112,6 +121,7 @@ describe('WeakIdentityMap', () => {
 
     const values = Array.from(map.values()).sort();
 
+    expect(map.size).toBe(2);
     expect(values.length).toBe(2);
     expect(values[0]).toBe(entity1);
     expect(values[1]).toBe(entity2);
@@ -126,6 +136,7 @@ describe('WeakIdentityMap', () => {
 
     const entries = Array.from(map.entries()).sort();
 
+    expect(map.size).toBe(2);
     expect(entries.length).toBe(2);
     expect(entries).toEqual(
       [