Typescript for events

[jthogsett]

Currently, all of the rhea interfaces that extend EventEmitter do not provide an EventMap generic argument, so event handlers do not have strong typings.

For example,

import { create_container } from 'rhea';

const container = create_container();
container.on('message', function (context) {
  // context is any and has no intellisense or type safety
});

If a generic event map argument is supplied to EventEmitter when extending it, we can get type safety and intellisense on all of the declared events, e.g.

// container.d.ts

type ContainerEvents = {
  'message': [EventContext]
  // add all container events here
};

interface Container extends EventEmitter<ContainerEvents> {
  // ...
}

This will give developers intellisense on event names when registering handlers to the EventEmitters and provide typings on the callback arguments.