simple-typed-events
Simple event emitter interface with full TypeScript support. Simply define your event names and their callbacks in an interface and pass it to createEventEmitter as a generic arg.
Function list:
-
createEventEmitter<T>()- returns an object with 4 functions-
on- Attach event listener -
off- Detach event listener -
once- Attach an event listener that will only fire once -
emit- Emit an event
-
import { createEventEmitter } from 'simple-typed-events';
interface Events {
start: () => void;
progress: (loaded: number, total: number) => void;
finish: () => void;
}
const emitter = createEventEmitter<Events>();
// attach event listener with on()
emitter.on('start', () => {});
// the Events interface can be used as a lookup type
const onProgress: Events['progress'] = (loaded, total) => {
// ...
};
emitter.on('progress', onProgress);
emitter.on('progress', (loaded, total) => {
// ...
});
emitter.once('finish', () => {
// ...
});
emitter.emit('progress'); // Typescript error! the args of the progress event must be passed
emitter.emit('progress', 3); // Still not legal. Both args must be passed
emitter.emit('progress', 3, 5); // no error
// detach listeners by reference
emitter.off('progress', onProgress);