Does TypeScript support events on classes?

Question

I am just wondering if in TypeScript you can define custom events on your classes or interfaces?

What would this look like?

Answer 1

Here's a simple example of adding custom-type events to your class, using sub-events:

class MyClass {

    readonly onMessage: SubEvent = new SubEvent();
    readonly onData: SubEvent = new SubEvent();

    sendMessage(msg: string) {
        this.onMessage.emit(msg);
    }

    sendData(data: MyCustomType) {
        this.onData.emit(data);
    }
}

And then any client can subscribe to receive those events:

const a = new MyClass();

const sub1 = a.onMessage.subscribe(msg => {
    // msg here is strongly-typed
});

const sub2 = a.onData.subscribe(data => {
    // data here is strongly-typed
});

And when you no longer need the events, you can cancel the subscriptions:

sub1.cancel();

sub2.cancel();