Class EventEmitterOfT

packages/alphatab/src/EventEmitter.ts:78–107

 * @internal
 */
export class EventEmitterOfT<T> implements IEventEmitterOfT<T> {
    private _listeners: ((arg: T) => void)[] = [];
    private readonly _fireOnRegister: (() => T | null) | undefined;

    public constructor(fireOnRegister: (() => T | null) | undefined = undefined) {
        this._fireOnRegister = fireOnRegister;
    }
    public on(value: (arg: T) => void): () => void {
        this._listeners.push(value);
        if (this._fireOnRegister) {
            const arg = this._fireOnRegister();
            if (arg !== null) {
                value(arg);
            }
        }
        return () => {
            this.off(value);
        };
    }

    public off(value: (arg: T) => void): void {
        this._listeners = this._listeners.filter(l => l !== value);
    }

    public trigger(arg: T): void {
        for (const l of this._listeners) {
            l(arg);
        }
    }
}