event-emitters/dist.es2018/EventEmitterWithOptionalCurrent.js

event emitters

import { EventEmitter } from './EventEmitter';
/**
 * This is the same as EventEmitterWithCurrent but the "current value" is optional
 */
export class EventEmitterWithOptionalCurrent extends EventEmitter {
    constructor(initialMessage) {
        super();
        if (arguments.length) {
            this.currentMessage = initialMessage;
            this.hasCurrentMessage = true;
        }
        else {
            this.hasCurrentMessage = false;
        }
    }
    emit(newMessage) {
        this.hasCurrentMessage = true;
        this.currentMessage = newMessage;
        super.emit(newMessage);
    }
    subscribe(listener) {
        super.subscribe(listener);
        if (this.hasCurrentMessage) {
            // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
            listener(this.currentMessage);
        }
        return listener;
    }
}
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