What are Event Emitters and how it works in Angular 2

Angular 2 doesn’t have bi-directional digest cycle, unlike angular 1. In angular 2, any change occurred in the component always gets propagated from the current component to all its children in hierarchy. If the change from one component needs to be reflected to any of its parent component in hierarchy, we can emit the event by using Event Emitter api.

In short, EventEmitter is class defined in @angular/core module which can be used by components and directives to emit custom events.

@output() somethingChanged = new EventEmitter();

We use somethingChanged.emit(value) method to emit the event. This is usually done in setter when the value is being changed in the class.

This event emit can be subscribed by any component of the module by using subscribe method.

myObj.somethingChanged.subscribe(val) => this.myLocalMethod(val));