Simplify event emitter

Author: dy

src/Emitter.js

@@ -1,22 +1,33 @@
-// EventTarget mixin — shared by DspObject and AudioPort
-// Adds on/off/once/emit/removeAllListeners/listenerCount to any EventTarget subclass
+// Tiny event emitter — extends EventTarget for instanceof conformance,
+// but overrides addEventListener/removeEventListener/dispatchEvent with own tracking.
+// No Node.js maxListeners warnings, no duplicate tracking, no platform dependency.
 
-export default (Base = EventTarget) => class Emitter extends Base {
-  #listeners = []
+export default () => class Emitter extends EventTarget {
+  #events = new Map()
 
-  on(type, fn) {
-    this.#listeners.push({ type, fn })
-    this.addEventListener(type, fn)
+  addEventListener(type, fn) {
+    if (!fn) return
+    let s = this.#events.get(type)
+    if (!s) this.#events.set(type, s = new Set())
+    s.add(fn)
   }
 
-  off(type, fn) {
-    this.#listeners = this.#listeners.filter(l => !(l.type === type && l.fn === fn))
-    this.removeEventListener(type, fn)
+  removeEventListener(type, fn) {
+    this.#events.get(type)?.delete(fn)
   }
 
+  dispatchEvent(event) {
+    let s = this.#events.get(event.type)
+    if (s) for (let fn of s) fn.call(this, event)
+    return true
+  }
+
+  on(type, fn) { this.addEventListener(type, fn) }
+  off(type, fn) { this.removeEventListener(type, fn) }
+
   once(type, fn) {
-    let wrapper = (e) => { fn(e); this.off(type, wrapper) }
-    this.on(type, wrapper)
+    let w = (e) => { fn(e); this.off(type, w) }
+    this.on(type, w)
   }
 
   emit(type, detail) {
@@ -25,17 +36,10 @@ export default (Base = EventTarget) => class Emitter extends Base {
     this.dispatchEvent(e)
   }
 
-  listenerCount(type) {
-    return this.#listeners.filter(l => l.type === type).length
-  }
+  listenerCount(type) { return this.#events.get(type)?.size || 0 }
 
   removeAllListeners(type) {
-    if (type) {
-      for (let l of this.#listeners) if (l.type === type) this.removeEventListener(l.type, l.fn)
-      this.#listeners = this.#listeners.filter(l => l.type !== type)
-    } else {
-      for (let l of this.#listeners) this.removeEventListener(l.type, l.fn)
-      this.#listeners = []
-    }
+    if (type) this.#events.delete(type)
+    else this.#events.clear()
   }
 }

test/audit-fixes.test.js

@@ -134,6 +134,26 @@ test('listener cleanup > disconnect only removes own handler', () => {
   is(output.listenerCount('_numberOfChannels'), 0, 'all cleaned up')
 })
 
+test('listener cleanup > fan-out beyond 10 connections emits no warning', () => {
+  let ctx = { sampleRate: 44100 }
+  let output = new AudioOutput(ctx, {}, 0)
+  let inputs = Array.from({ length: 16 }, () =>
+    new AudioInput(ctx, { channelCount: 1, channelCountMode: 'max', channelInterpretation: 'discrete' }, 0))
+
+  // connect 16 inputs to same output — must not trigger MaxListenersExceededWarning
+  let warned = false
+  let onWarn = (w) => { if (w.name === 'MaxListenersExceededWarning') warned = true }
+  process.on('warning', onWarn)
+  for (let inp of inputs) inp.connect(output)
+  is(output.listenerCount('_numberOfChannels'), 16, '16 listeners registered')
+  ok(!warned, 'no MaxListenersExceededWarning')
+
+  // cleanup
+  for (let inp of inputs) inp.disconnect(output)
+  is(output.listenerCount('_numberOfChannels'), 0, 'all cleaned up after disconnect')
+  process.off('warning', onWarn)
+})
+
 test.mute('cancelScheduledValues > removes future events', () => {
   let ctx = { currentTime: 0, sampleRate: 44100 }
   let p = new AudioParam(ctx, 0, 'a')