Usage

In the Setup, we've added two events to our class (MyClass). We're now ready to attach event listeners and emit events.

Adding Listeners

Listeners can be attached using the on(), once() and addListener() methods:

import { ESMitter, type ESMitterEvent } from "esm-itter";

class MyClass extends ESMitter<{
  'success': ESMitterEvent<[{ foo: string, bar: string }]>;
  'error': ESMitterEvent<[number, string]>;
}> {}

const instance = MyClass();

// Attach event listener using on()
instance.on('success', ({ foo, bar }) => { /* [...] */ })

// Attach event listener using addListener()
instance.addListener('success', ({ foo, bar }) => { /* [...] */ })

// Attach event listener using once()
instance.once('success', ({ foo, bar }) => { /* [...] */ })

Note that on() is merely an alias for addListener() and once() will make sure a listener is only called once and the discarded.

The parameters passed to the listener are typed according to the list of events we provided to the ESMitter class.

Removing Listeners

Listeners can be removed using the off(), removeListener() and removeAllListeners() methods:

// Remove all listeners for the 'success' event using off()
instance.off("success");

// Remove all listeners for the 'success' event using removeListener()
instance.removeListener("success");

// Remove all listeners for the 'success' event using removeAllListeners()
instance.removeAllListeners("success");

// Remove all listeners for all events (like a reset) using removeAllListeners()
instance.removeAllListeners();

// Remove a specific listener using off() and referencing the listener itself
const listener = ({ foo, bar }) => {
  /* [...] */
};
instance.on("success", listener);
instance.off("success", listener);

Note that off() (like on(), respectively) is merely an alias for removeListener().