How to prevent that event is emitted from outside? - node.js

Question

Imagine I had a simple counting process that acts as a default Node EventEmitter:
import {EventEmitter} from 'events';
async function sleep(milliseconds: number): Promise<void> {
return new Promise((resolve) => setTimeout(resolve, milliseconds));
}
class MyCountingProcess extends EventEmitter {
public async start() {
for (let i = 0; i <= 10; i++) {
this.emit('counting', i);
await sleep(1000); // just some demo async function
}
}
}
const myCountingProcess = new MyCountingProcess();
myCountingProcess.on('counting', (value) => {
console.log("current value is: " + value);
});
myCountingProcess.start();
So far, everything works as intended.
What puzzles me however is that I could very easily disturb this logic by adding another line outside MyCountingProcess (after myCountingProcess.start()) like
myCountingProcess.emit(666);
Then suddenly, the exact same process would no longer work as intended.
Is this intentional? Or bad architectural design? Or am I using the EventEmitter pattern wrong?
It would make much more sense to me if emit could only be called by the EventEmitter (i.e. within it), not on it. Or at least if it could be made a private method in TypeScript, although that would of course only be syntax.
So what would one usually do to prevent scenarios like this one?

Answer 1

Because MyCountingProcess is extending EventEmitter, it will behave as an EventEmmiter instance, unless you override the event methods.
For your use case, I recommend adding the EventEmmiter as a variable inside MyCountingProcess like this:
import { EventEmitter } from 'events';
class MyCountingProcess {
#events: EventEmitter
constructor() {
this.#events = new EventEmitter()
}
public async start() {
for (let i = 0; i <= 10; i++) {
this.#events.emit('counting', i);
await sleep(1000);
}
}
public on(event: string | symbol, listener: (...args: any[]) => void) {
return this.#events.on(event, listener)
}
}
const myCountingProcess = new MyCountingProcess();
myCountingProcess.on('counting', (value) => {
console.log("current value is: " + value);
});
myCountingProcess.start();