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EventTarget.ts
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EventTarget.ts
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export type EventHandler<EventT> = (ev?: EventT) => void;
type HandlersMap<EventT> = Map<string, EventHandler<EventT>[]>;
export interface ObservableInterface<EventT = any> {
on(eventName: string, handler: EventHandler<EventT>): this;
once(eventName: string, handler: EventHandler<EventT>): this;
off(eventName: string, handler: EventHandler<EventT>): this;
}
export class EventTarget<EventT = any> implements ObservableInterface<EventT> {
protected events: HandlersMap<EventT> = new Map<string, EventHandler<EventT>[]>();
protected onceEvents: HandlersMap<EventT> = new Map<string, EventHandler<EventT>[]>();
public on(eventName: string, handler: EventHandler<EventT>): this {
this.addHandler(this.events, eventName, handler);
return this;
}
public once(eventName: string, handler: EventHandler<EventT>): this {
this.addHandler(this.onceEvents, eventName, handler);
return this;
}
public off(eventName: string, handler: EventHandler<EventT>): this {
const index = this.events.get(eventName)?.indexOf(handler);
if (!index || index < 0) {
return this;
}
this.events.get(eventName).splice(index, 1);
}
public emit(eventName: string, event?: EventT): this {
this.callHandlers(this.events, eventName, event);
this.callHandlers(this.onceEvents, eventName, event);
this.onceEvents.delete(eventName);
return this;
}
private addHandler(map: HandlersMap<EventT>, eventName: string, handler: EventHandler<EventT>): void {
const handlers = map.get(eventName) ?? [];
handlers.push(handler);
map.set(eventName, handlers);
}
private callHandlers(map: HandlersMap<EventT>, eventName: string, event: EventT): void {
map.get(eventName)?.forEach(callback => callback(event));
}
}