README.md

@wopjs/event

A tiny utility to create an event that can be subscribed to.

Install

npm add @wopjs/event

Usage

import { event, send } from "@wopjs/event";

const onDidChange = event<string>();
const dispose = onDidChange(data => console.log(data));

send(onDidChange, "data"); // logs "data"
dispose();

Patterns

In general, you would export the event directly (which is the AddEventListener type) and send it from the class that owns it.

// module-a.ts

import { event, send } from "@wopjs/event";
import { disposableStore } from "@wopjs/disposable";

export class A {
  public readonly dispose = disposableStore();

  public readonly onStatusDidChange = event<string>();

  public constructor() {
    this.dispose.add(this.onStatusDidChange);

    this.dispose.add(
      onOtherEvent(() => {
        send(this.onStatusDidChange, "loading");
      })
    );
  }
}

Other modules can then subscribe to the event, but generally not send it.

// module-b.ts

import type { A } from "./module-a";
import { event, send } from "@wopjs/event";
import { disposableStore } from "@wopjs/disposable";

export class B {
  public readonly dispose = disposableStore();

  public constructor(a: A) {
    this.dispose.add(
      a.onStatusDidChange(status => {
        console.log(status);
      })
    );
  }
}

You can also let module-b depend only on the event itself so that it does not need to import module-a (hence more "pure").

In this case generally you would use the simpler IEvent type to define the event.

// module-b.ts

import { event, send, IEvent } from "@wopjs/event";
import { disposableStore } from "@wopjs/disposable";

export class B {
  public readonly dispose = disposableStore();

  public constructor(onAStatusDidChange: IEvent<string>) {
    this.dispose.add(
      onAStatusDidChange(status => {
        console.log(status);
      })
    );
  }
}

If you need to let other modules send the event, it is recommended to expose a dedicated method for that.

// module-a.ts

import { event, send } from "@wopjs/event";
import { disposableStore } from "@wopjs/disposable";

export class A {
  public readonly dispose = disposableStore();

  public readonly onStatusDidChange = event<string>();

  public constructor() {
    this.dispose.add(onStatusDidChange);
  }

  public changeStatus(status: string) {
    send(this.onStatusDidChange, status);
  }
}

License

MIT @ wopjs