feat(timed-memoize): additional memoize decorator with timeout

src/decorators/memoize/memoize.ts

@@ -5,15 +5,17 @@ export function Memoize(hashFn?: (...args: any[]) => string) {
 }
 
 function decorator(fn: (...args: any[]) => any, hashFn?: (...args: any[]) => string) {
-  const cache: { [key: string]: any } = {};
+  const cache: { [key: string]: { value: string } } = {};
 
   return function(...args: any[]) {
-    const hash = hashFn ? hashFn.apply(this, args) : JSON.stringify(args);
+    const key = hashFn ? hashFn.apply(this, args) : JSON.stringify(args);
 
-    if (!isUndefined(cache[hash])) {
-      return cache[hash];
+    if (!isUndefined(cache[key])) {
+      return cache[key].value;
     }
 
-    return (cache[hash] = fn.apply(this, args));
+    cache[key] = { value: fn.apply(this, args) };
+
+    return cache[key].value;
   };
 }

src/decorators/timed-memoize/timed-memoize.spec.ts

@@ -0,0 +1,22 @@
+import { TimedMemoize } from './timed-memoize';
+
+class TestTimedMemoize {
+  counter = 0;
+
+  @TimedMemoize(2000)
+  count(...args: any[]) {
+    return ++this.counter;
+  }
+}
+
+describe('TimedMemoize', () => {
+  it('should really invalidate cache',() => {
+    const past = Date.now() + 50000;
+    const test = new TestTimedMemoize();
+    expect(test.count(1)).toEqual(1);
+
+    jest.spyOn(Date, 'now').mockImplementation(() => past);
+
+    expect(test.count(1)).toEqual(2);
+  });
+});

src/decorators/timed-memoize/timed-memoize.ts

@@ -0,0 +1,34 @@
+import { generateFunctionDecorator, isUndefined } from '../../helpers/general';
+
+interface ITimedMemoizeProps {
+  hashFn?: (...args: any[]) => string,
+  invalidateOnTimeout?: boolean
+}
+
+export function TimedMemoize(timeoutMs: number, props: ITimedMemoizeProps = {}) {
+  return generateFunctionDecorator('TimedMemoize', decorator, timeoutMs, props);
+}
+
+function decorator<T>(fn: (...args: any[]) => any, timeoutMs: number, { hashFn, invalidateOnTimeout }: ITimedMemoizeProps) {
+  const cache: { [key: string]: { value: string, timeoutTimestamp: number } } = {};
+
+  return function(...args: any[]) {
+    const now = Date.now();
+    const key = hashFn ? hashFn.apply(this, args) : JSON.stringify(args);
+
+    if (!isUndefined(cache[key]) && cache[key].timeoutTimestamp > now) {
+      return cache[key].value;
+    }
+
+    cache[key] = {
+      value: fn.apply(this, args),
+      timeoutTimestamp: now + timeoutMs
+    };
+
+    if (invalidateOnTimeout) {
+      setTimeout(() => delete cache[key], timeoutMs);
+    }
+
+    return cache[key].value;
+  };
+}