fix(esl-utils): incorrect throttle behaviour

src/modules/esl-event-listener/test/targets/decorator.test.ts

@@ -141,6 +141,7 @@ describe('ESLEventUtils.decorate proxy', () => {
       window.dispatchEvent(event);
       jest.advanceTimersByTime(10);
       expect(fn).lastCalledWith(event);
+      jest.advanceTimersByTime(DEFAULT_TIMEOUT + 100);
     });
 
     test('Proxy scroll happens throttled (multiple events received once in bounds of threshold)',  ()=> {

src/modules/esl-utils/async/test/throttle.test.ts

@@ -17,7 +17,7 @@ describe('async/throttle', () => {
     jest.advanceTimersByTime(100);
     expect(fn).toBeCalledTimes(2);
     expect(throttled()).toBeUndefined();
-    expect(fn).toBeCalledTimes(3);
+    expect(fn).toBeCalledTimes(2);
   });
 
   test('test context', () => {

src/modules/esl-utils/async/throttle.ts

@@ -26,21 +26,21 @@ export function throttle<F extends AnyToAnyFnSignature>(fn: F, threshold = 250,
 
   function throttledSubject(...args: any[]): void {
     const now = Date.now();
+    const lastThreshold = last + threshold;
 
-    if (!last || now >= last + threshold) {
-      last = now;
-      fn.apply(this, args);
-    }
+    deferred = createDeferred();
 
-    deferred = deferred || createDeferred();
-    (typeof timeout === 'number') && clearTimeout(timeout);
-    timeout = window.setTimeout(() => {
+    if (!last || now >= lastThreshold) {
       last = now;
-      timeout = null;
-      // fn.apply to save call context
-      deferred!.resolve(fn.apply(thisArg || this, args));
-      deferred = null;
-    }, threshold);
+      deferred.resolve(fn.apply(thisArg || this, args));
+    } else {
+      (typeof timeout === 'number') && clearTimeout(timeout);
+      timeout = window.setTimeout(() => {
+        last = Date.now();
+        timeout = null;
+        deferred!.resolve(fn.apply(thisArg || this, args));
+      }, lastThreshold - now);
+    }
   }
   Object.defineProperty(throttledSubject, 'promise', {
     get: () => deferred ? deferred.promise : Promise.resolve()