chore: EventEmitter should mimic NodeJS' one (#10241)

docs/api/puppeteer.commoneventemitter.addlistener.md

@@ -8,7 +8,7 @@ sidebar_label: CommonEventEmitter.addListener
 
 ```typescript
 interface CommonEventEmitter {
-  addListener(event: EventType, handler: Handler): CommonEventEmitter;
+  addListener(event: EventType, handler: Handler): this;
 }
 ```
 
@@ -21,4 +21,4 @@ interface CommonEventEmitter {
 
 **Returns:**
 
-[CommonEventEmitter](./puppeteer.commoneventemitter.md)
+this

docs/api/puppeteer.commoneventemitter.off.md

@@ -8,7 +8,7 @@ sidebar_label: CommonEventEmitter.off
 
 ```typescript
 interface CommonEventEmitter {
-  off(event: EventType, handler: Handler): CommonEventEmitter;
+  off(event: EventType, handler: Handler): this;
 }
 ```
 
@@ -21,4 +21,4 @@ interface CommonEventEmitter {
 
 **Returns:**
 
-[CommonEventEmitter](./puppeteer.commoneventemitter.md)
+this

docs/api/puppeteer.commoneventemitter.on.md

@@ -8,7 +8,7 @@ sidebar_label: CommonEventEmitter.on
 
 ```typescript
 interface CommonEventEmitter {
-  on(event: EventType, handler: Handler): CommonEventEmitter;
+  on(event: EventType, handler: Handler): this;
 }
 ```
 
@@ -21,4 +21,4 @@ interface CommonEventEmitter {
 
 **Returns:**
 
-[CommonEventEmitter](./puppeteer.commoneventemitter.md)
+this

docs/api/puppeteer.commoneventemitter.once.md

@@ -8,7 +8,7 @@ sidebar_label: CommonEventEmitter.once
 
 ```typescript
 interface CommonEventEmitter {
-  once(event: EventType, handler: Handler): CommonEventEmitter;
+  once(event: EventType, handler: Handler): this;
 }
 ```
 
@@ -21,4 +21,4 @@ interface CommonEventEmitter {
 
 **Returns:**
 
-[CommonEventEmitter](./puppeteer.commoneventemitter.md)
+this

docs/api/puppeteer.commoneventemitter.removealllisteners.md

@@ -8,7 +8,7 @@ sidebar_label: CommonEventEmitter.removeAllListeners
 
 ```typescript
 interface CommonEventEmitter {
-  removeAllListeners(event?: EventType): CommonEventEmitter;
+  removeAllListeners(event?: EventType): this;
 }
 ```
 
@@ -20,4 +20,4 @@ interface CommonEventEmitter {
 
 **Returns:**
 
-[CommonEventEmitter](./puppeteer.commoneventemitter.md)
+this

docs/api/puppeteer.commoneventemitter.removelistener.md

@@ -8,7 +8,7 @@ sidebar_label: CommonEventEmitter.removeListener
 
 ```typescript
 interface CommonEventEmitter {
-  removeListener(event: EventType, handler: Handler): CommonEventEmitter;
+  removeListener(event: EventType, handler: Handler): this;
 }
 ```
 
@@ -21,4 +21,4 @@ interface CommonEventEmitter {
 
 **Returns:**
 
-[CommonEventEmitter](./puppeteer.commoneventemitter.md)
+this

docs/api/puppeteer.eventemitter.addlistener.md

@@ -14,7 +14,7 @@ Add an event listener.
 
 ```typescript
 class EventEmitter {
-  addListener(event: EventType, handler: Handler<any>): EventEmitter;
+  addListener(event: EventType, handler: Handler<any>): this;
 }
 ```
 
@@ -27,4 +27,4 @@ class EventEmitter {
 
 **Returns:**
 
-[EventEmitter](./puppeteer.eventemitter.md)
+this

docs/api/puppeteer.eventemitter.off.md

@@ -10,7 +10,7 @@ Remove an event listener from firing.
 
 ```typescript
 class EventEmitter {
-  off(event: EventType, handler: Handler<any>): EventEmitter;
+  off(event: EventType, handler: Handler<any>): this;
 }
 ```
 
@@ -23,6 +23,6 @@ class EventEmitter {
 
 **Returns:**
 
-[EventEmitter](./puppeteer.eventemitter.md)
+this
 
 `this` to enable you to chain method calls.

docs/api/puppeteer.eventemitter.on.md

@@ -10,7 +10,7 @@ Bind an event listener to fire when an event occurs.
 
 ```typescript
 class EventEmitter {
-  on(event: EventType, handler: Handler<any>): EventEmitter;
+  on(event: EventType, handler: Handler<any>): this;
 }
 ```
 
@@ -23,6 +23,6 @@ class EventEmitter {
 
 **Returns:**
 
-[EventEmitter](./puppeteer.eventemitter.md)
+this
 
 `this` to enable you to chain method calls.

docs/api/puppeteer.eventemitter.once.md

@@ -10,7 +10,7 @@ Like `on` but the listener will only be fired once and then it will be removed.
 
 ```typescript
 class EventEmitter {
-  once(event: EventType, handler: Handler<any>): EventEmitter;
+  once(event: EventType, handler: Handler<any>): this;
 }
 ```
 
@@ -23,6 +23,6 @@ class EventEmitter {
 
 **Returns:**
 
-[EventEmitter](./puppeteer.eventemitter.md)
+this
 
 `this` to enable you to chain method calls.

docs/api/puppeteer.eventemitter.removealllisteners.md

@@ -10,7 +10,7 @@ Removes all listeners. If given an event argument, it will remove only listeners
 
 ```typescript
 class EventEmitter {
-  removeAllListeners(event?: EventType): EventEmitter;
+  removeAllListeners(event?: EventType): this;
 }
 ```
 
@@ -22,6 +22,6 @@ class EventEmitter {
 
 **Returns:**
 
-[EventEmitter](./puppeteer.eventemitter.md)
+this
 
 `this` to enable you to chain method calls.

docs/api/puppeteer.eventemitter.removelistener.md

@@ -14,7 +14,7 @@ Remove an event listener.
 
 ```typescript
 class EventEmitter {
-  removeListener(event: EventType, handler: Handler<any>): EventEmitter;
+  removeListener(event: EventType, handler: Handler<any>): this;
 }
 ```
 
@@ -27,4 +27,4 @@ class EventEmitter {
 
 **Returns:**
 
-[EventEmitter](./puppeteer.eventemitter.md)
+this

docs/api/puppeteer.page.off.md

@@ -11,7 +11,7 @@ class Page {
   off<K extends keyof PageEventObject>(
     eventName: K,
     handler: (event: PageEventObject[K]) => void
-  ): EventEmitter;
+  ): this;
 }
 ```
 
@@ -24,4 +24,4 @@ class Page {
 
 **Returns:**
 
-[EventEmitter](./puppeteer.eventemitter.md)
+this

docs/api/puppeteer.page.on.md

@@ -19,7 +19,7 @@ class Page {
   on<K extends keyof PageEventObject>(
     eventName: K,
     handler: (event: PageEventObject[K]) => void
-  ): EventEmitter;
+  ): this;
 }
 ```
 
@@ -32,4 +32,4 @@ class Page {
 
 **Returns:**
 
-[EventEmitter](./puppeteer.eventemitter.md)
+this

docs/api/puppeteer.page.once.md

@@ -11,7 +11,7 @@ class Page {
   once<K extends keyof PageEventObject>(
     eventName: K,
     handler: (event: PageEventObject[K]) => void
-  ): EventEmitter;
+  ): this;
 }
 ```
 
@@ -24,4 +24,4 @@ class Page {
 
 **Returns:**
 
-[EventEmitter](./puppeteer.eventemitter.md)
+this

packages/puppeteer-core/src/api/Locator.ts

@@ -109,22 +109,22 @@ export class Locator extends EventEmitter {
   override on<K extends keyof LocatorEventObject>(
     eventName: K,
     handler: (event: LocatorEventObject[K]) => void
-  ): Locator {
-    return super.on(eventName, handler) as Locator;
+  ): this {
+    return super.on(eventName, handler);
   }
 
   override once<K extends keyof LocatorEventObject>(
     eventName: K,
     handler: (event: LocatorEventObject[K]) => void
-  ): Locator {
-    return super.once(eventName, handler) as Locator;
+  ): this {
+    return super.once(eventName, handler);
   }
 
   override off<K extends keyof LocatorEventObject>(
     eventName: K,
     handler: (event: LocatorEventObject[K]) => void
-  ): Locator {
-    return super.off(eventName, handler) as Locator;
+  ): this {
+    return super.off(eventName, handler);
   }
 
   /**

packages/puppeteer-core/src/api/Page.ts

@@ -480,7 +480,7 @@ export class Page extends EventEmitter {
   override on<K extends keyof PageEventObject>(
     eventName: K,
     handler: (event: PageEventObject[K]) => void
-  ): EventEmitter {
+  ): this {
     if (eventName === 'request') {
       const wrap =
         this.#handlerMap.get(handler) ||
@@ -500,7 +500,7 @@ export class Page extends EventEmitter {
   override once<K extends keyof PageEventObject>(
     eventName: K,
     handler: (event: PageEventObject[K]) => void
-  ): EventEmitter {
+  ): this {
     // Note: this method only exists to define the types; we delegate the impl
     // to EventEmitter.
     return super.once(eventName, handler);
@@ -509,7 +509,7 @@ export class Page extends EventEmitter {
   override off<K extends keyof PageEventObject>(
     eventName: K,
     handler: (event: PageEventObject[K]) => void
-  ): EventEmitter {
+  ): this {
     if (eventName === 'request') {
       handler = this.#handlerMap.get(handler) || handler;
     }

packages/puppeteer-core/src/common/EventEmitter.ts

@@ -29,19 +29,19 @@ export type Handler<T = unknown> = (event: T) => void;
  * @public
  */
 export interface CommonEventEmitter {
-  on(event: EventType, handler: Handler): CommonEventEmitter;
-  off(event: EventType, handler: Handler): CommonEventEmitter;
+  on(event: EventType, handler: Handler): this;
+  off(event: EventType, handler: Handler): this;
   /* To maintain parity with the built in NodeJS event emitter which uses removeListener
    * rather than `off`.
    * If you're implementing new code you should use `off`.
    */
-  addListener(event: EventType, handler: Handler): CommonEventEmitter;
-  removeListener(event: EventType, handler: Handler): CommonEventEmitter;
+  addListener(event: EventType, handler: Handler): this;
+  removeListener(event: EventType, handler: Handler): this;
   emit(event: EventType, eventData?: unknown): boolean;
-  once(event: EventType, handler: Handler): CommonEventEmitter;
+  once(event: EventType, handler: Handler): this;
   listenerCount(event: string): number;
 
-  removeAllListeners(event?: EventType): CommonEventEmitter;
+  removeAllListeners(event?: EventType): this;
 }
 
 /**
@@ -73,7 +73,7 @@ export class EventEmitter implements CommonEventEmitter {
    * @param handler - the function to be called when the event occurs.
    * @returns `this` to enable you to chain method calls.
    */
-  on(event: EventType, handler: Handler<any>): EventEmitter {
+  on(event: EventType, handler: Handler<any>): this {
     this.emitter.on(event, handler);
     return this;
   }
@@ -84,7 +84,7 @@ export class EventEmitter implements CommonEventEmitter {
    * @param handler - the function that should be removed.
    * @returns `this` to enable you to chain method calls.
    */
-  off(event: EventType, handler: Handler<any>): EventEmitter {
+  off(event: EventType, handler: Handler<any>): this {
     this.emitter.off(event, handler);
     return this;
   }
@@ -93,7 +93,7 @@ export class EventEmitter implements CommonEventEmitter {
    * Remove an event listener.
    * @deprecated please use {@link EventEmitter.off} instead.
    */
-  removeListener(event: EventType, handler: Handler<any>): EventEmitter {
+  removeListener(event: EventType, handler: Handler<any>): this {
     this.off(event, handler);
     return this;
   }
@@ -102,7 +102,7 @@ export class EventEmitter implements CommonEventEmitter {
    * Add an event listener.
    * @deprecated please use {@link EventEmitter.on} instead.
    */
-  addListener(event: EventType, handler: Handler<any>): EventEmitter {
+  addListener(event: EventType, handler: Handler<any>): this {
     this.on(event, handler);
     return this;
   }
@@ -125,7 +125,7 @@ export class EventEmitter implements CommonEventEmitter {
    * @param handler - the handler function to run when the event occurs
    * @returns `this` to enable you to chain method calls.
    */
-  once(event: EventType, handler: Handler<any>): EventEmitter {
+  once(event: EventType, handler: Handler<any>): this {
     const onceHandler: Handler<any> = eventData => {
       handler(eventData);
       this.off(event, onceHandler);
@@ -150,7 +150,7 @@ export class EventEmitter implements CommonEventEmitter {
    * @param event - the event to remove listeners for.
    * @returns `this` to enable you to chain method calls.
    */
-  removeAllListeners(event?: EventType): EventEmitter {
+  removeAllListeners(event?: EventType): this {
     if (event) {
       this.eventsMap.delete(event);
     } else {

packages/puppeteer-core/src/common/bidi/BidiOverCDP.ts

@@ -20,7 +20,7 @@ import type {ProtocolMapping} from 'devtools-protocol/types/protocol-mapping.js'
 
 import {CDPSession, Connection as CDPPPtrConnection} from '../Connection.js';
 import {TargetCloseError} from '../Errors.js';
-import {Handler} from '../EventEmitter.js';
+import {EventEmitter, Handler} from '../EventEmitter.js';
 
 import {Connection as BidiPPtrConnection} from './Connection.js';
 
@@ -107,7 +107,7 @@ class CDPConnectionAdapter {
  *
  * @internal
  */
-class CDPClientAdapter<T extends Pick<CDPPPtrConnection, 'send' | 'on' | 'off'>>
+class CDPClientAdapter<T extends EventEmitter & Pick<CDPPPtrConnection, 'send'>>
   extends BidiMapper.EventEmitter<CdpEvents>
   implements BidiMapper.CdpClient
 {