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yatishbalaji/PubSub.ts

Last active September 3, 2021 12:04
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custom JS pubsub
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PubSub.ts
export interface IPubSubOptions {
maxListeners?: number;
}
export class PubSub {
private maxListeners: number;
private listenerCount: number;
private eventListeners: Map<string, Function[]>;
constructor(options: IPubSubOptions) {
this.maxListeners = options.maxListeners || 1000;
this.listenerCount = 0;
}
setMaxListeners(listenerCount: number): PubSub {
this.maxListeners = listenerCount;
return this;
}
private setListenerCount(count: number): void {
this.listenerCount = count;
}
getListenerCount(): number {
return this.listenerCount;
}
getEventListenerCount(event: string): number {
return (this.eventListeners.get(event) || []).length;
}
on(event: string, fn: Function): PubSub {
if (this.getListenerCount() === this.maxListeners) {
console.log('Number of listeners exceded maxListeners set');
return this;
}
const listeners = this.eventListeners.get(event) || [];
listeners.push(fn);
this.eventListeners.set(event, listeners);
this.setListenerCount(this.listenerCount + 1);
return this;
}
off(event: string, fn: Function): PubSub {
const listeners = this.eventListeners.get(event);
if (!listeners) return this;
const len = listeners.length;
for (let i = 0; i < len; i++) {
if (listeners[i] === fn) {
listeners.splice(i, 1);
this.setListenerCount(this.listenerCount - 1);
break;
}
}
return this;
}
once(event: string, fn: Function): PubSub {
if (this.getListenerCount() === this.maxListeners) {
console.log('Number of listeners exceded maxListeners set');
return this;
}
const listeners = this.eventListeners.get(event) || [];
const innerFn = (...args: IArguments[]) => {
fn(...args);
this.off(event, fn);
};
listeners.push(innerFn);
this.eventListeners.set(event, listeners);
this.setListenerCount(this.listenerCount + 1);
return this;
}
emit(event: string, ...args: IArguments[]): boolean {
const listeners = this.eventListeners.get(event);
if (!listeners) return false;
listeners.forEach(fn => fn(...args));
return true;
}
}
@yatishbalaji
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yatishbalaji commented Sep 3, 2021 •
edited
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cont emitterOptions: IPubSubOptions = {
maxListeners: 10000,
}

const emitter = new PubSub(emitterOptions);
emitter.on('msg', (data) => console.log(data));
emitter.once('delete', (id) => console.log('deleted id'));

emitter.emit('msg', 'testing');

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