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javascriptnode.jsclasseventemitter
Elliot
Elliot

Reputation: 1983

nodejs events - EventEmitter - understanding class instances

I am instantiating an event emitter and noticed that both of these lines seem to work fine.

Could anyone clarify tradeoffs or differences between these two ways to import and instantiate the EventEmitter class?

1: var eventEmitter = new (require('events')).EventEmitter();

2: var eventEmitter = new (require('events').EventEmitter)();

My take:

In 1, (require('events')) should return the exports of the events module. Then .EventEmitter() references that class and new create a new instance of EventEmitter.

In 2, (require('events').EventEmitter) should return the exported EventEmitter class. Thennew...()creates a new instance ofEventEmitter`.

Upvotes: 1

Views: 200

Answers (1)

Azamantes
Azamantes

Reputation: 1461

It is nothing unusual. You can put as many parentheses as you like around a function and then () after it and it will just work.

It's similar to

(1 + 2) === 3;
((1) + 2) === 3;
((1 + (2))) === (3);

etc... The same applies to objects/functions.

class MyClass { /* ... */ }

const object = {
    c: MyClass,
};
let a = new object.c();

console.log(a === new (object).c());
console.log(a === new ((object.c))());
console.log(a === new ((object).c)());

etc...

It's worth noticing what you cannot put parenthese after a dot ., so for example:

let a = new object.(c)();

would throw an error.

Upvotes: 1

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