@sbspk/disposable v1.0.4

This is a simple library for implementing event subscription APIs.

Implementing Event Subscription APIs

const { Emitter } = require("@sbspk/disposable");

class User {
  constructor() {
    this.emitter = new Emitter();
  }

  onDidChangeName(callback) {
    this.emitter.on("did-change-name", callback);
  }

  setName(name) {
    if (name !== this.name) {
      this.name = name;
      this.emitter.emit("did-change-name", name);
    }

    return this.name;
  }

  destroy() {
    this.emitter.dispose();
  }
}

In the example above, we implement ::onDidChangeName on the user object, which will register callbacks to be invoked whenever the user's name changes. To do so, we make use of an internal Emitter instance. We use ::on to subscribe the given callback in ::onDidChangeName, and ::emit in ::setName to notify subscribers. Finally, when the User instance is destroyed we call ::dispose on the emitter to unsubscribe all subscribers.

Consuming Event Subscription APIs

Emitter::on returns a Disposable instance, which has a ::dispose method. To unsubscribe, simply call dispose on the returned object.

const subscription = user.onDidChangeName((name) =>
  console.log(`My name is ${name}`)
);

// Later, to unsubscribe...
subscription.dispose();

You can also use CompositeDisposable to combine disposable instances together.

const { CompositeDisposable } = require('@sbspk/disposable')

const subscriptions = new CompositeDisposable()
subscriptions.add(user1.onDidChangeName((name) => console.log(`User 1: ${name}`))
subscriptions.add(user2.onDidChangeName((name) => console.log(`User 2: ${name}`))

// Later, to unsubscribe from *both*...
subscriptions.dispose()

Creating Your Own Disposables

Disposables are convenient ways to represent a resource you will no longer need at some point. You can instantiate a disposable with an action to take when no longer needed.

const { Disposable } = require("@sbspk/disposable");

const disposable = new Disposable(() => this.destroyResource());