Hi, just letting you know that you're linking to a 404 LICENSE file in the readme: https://github.com/lukas-reining/eventsource/blob/main/LICENSE

When a working EventSource is failed (by the remote end closing the connection), reconnect() is called internally as expected.

reconnect() checks whether readyState has been set to CLOSED (it hasn't), and then queues a call to connect() after a timeout:

Before the timeout expires, the consuming application calls close(), which changes the readyState to CLOSED.

Once the timeout expires, connect() resets readyState to CONNECTING:

.. and the previously closed EventSource begins emitting messages.

A quick fix might be to test readyState early in connect() or to store the timeoutID returned by reconnect()'s setTimeout() and call clearTimeout() during close().

When setting disableRetry to true in the config and an event happens that would trigger a retry, the library still logs a warning to the console, although the retry will not happen due to the disableRetry option in the config.
This is a bit confusing. The warning tells the developer it will reconnect to the event-source, while actually not doing so.

I think it should not log the warning in this case. Or is this expected behaviour?

https://github.com/lukas-reining/eventsource/blob/ad8eb89b52cf6ae98338638af91faf6ceb20b247/src/eventsource.ts#L146C1-L153C1

Using "type": "module" in package.json, results in the following behavior. Hers's a minimally viable example:

Node version 18.19.1
extended-eventsource@^1.4.6

ESM

index.js

import { EventSource } from 'extended-eventsource';

const es = new EventSource(<MY_SSE_URL>, {
  withCredentials: true,
  disableLogger: true,
});

es.onopen = () => {
  console.log('EventSource connected');
};

Error (via node index.js)

import { EventSource } from 'extended-eventsource';
         ^^^^^^^^^^^
SyntaxError: Named export 'EventSource' not found. The requested module 'extended-eventsource' is a CommonJS module, which may not support all module.exports as named exports.
CommonJS modules can always be imported via the default export, for example using:

import pkg from 'extended-eventsource';
const { EventSource } = pkg;

    at ModuleJob._instantiate (node:internal/modules/esm/module_job:123:21)
    at async ModuleJob.run (node:internal/modules/esm/module_job:191:5)
    at async ModuleLoader.import (node:internal/modules/esm/loader:336:24)
    at async loadESM (node:internal/process/esm_loader:34:7)
Node.js v18.19.1dleMainPromise (node:internal/modules/run_main:106:12)

The suggested "fix" from the error no effect, and result in the following:

Modified index.js

import pkg from 'extended-eventsource';
const { EventSource } = pkg;

const es = new EventSource('https://sdk.flagsync.com/events/sdk-updates', {
  withCredentials: true,
  disableLogger: true,
});

es.onopen = () => {
  console.log('EventSource connected');
};

export { CustomEventSource, CustomEventSource as EventSource };
^^^^^^

SyntaxError: Unexpected token 'export'
    at internalCompileFunction (node:internal/vm:73:18)
    at wrapSafe (node:internal/modules/cjs/loader:1274:20)
    at Module._compile (node:internal/modules/cjs/loader:1320:27)

Package.json

{
  "name": "modern",
  "version": "1.0.0",
  "description": "",
  "main": "index",
  "type": "module",
  "scripts": {
    "start": "node index.js"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "dependencies": {
    "extended-eventsource": "^1.4.6"
  }
}

CJS

Require

require does work as expected; must remove "type": "module" from package.json

index.js

const { EventSource } = require('extended-eventsource');

const es = new EventSource(<MY_SSE_URL>, {
  withCredentials: true,
  disableLogger: true,
});

es.onopen = () => {
  console.log('EventSource connected');
};

EventSource connected

package.json

{
  "name": "scripts",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "start": "node index.js"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "dependencies": {
    "extended-eventsource": "^1.4.6"
  }
}

The eventsource repository currently lists core-js as a dependency, but it seems to be unused throughout the codebase. I suggest removing this dependency to streamline the project.

Thanks for creating such a wonderful package, @lukas-reining
I was trying to use sse in my angular app, but couldn't set Authorization header for request, and I found this package, really helpful.
By the way, why does it send empty string "" as the first data?
Of course, this is not a big issue, but as I was trying to send json string from backend and parse it on frontend, I encountered this, which caught me for some time.
Of course I added validation logic to avoid error, but I just want this package to be perfect.

This is working fine on local development, when I run angular app on localhost:4200,
However, once I deploy the app to the vercel, it returns error.

main-6FYVCRR5.js:7 ERROR TypeError: (void 0) is not a constructor
    at e.getEventSource (main-6FYVCRR5.js:18:4128)
    at i._subscribe (main-6FYVCRR5.js:18:3856)
    at i._trySubscribe (main-6FYVCRR5.js:3:4428)
    at main-6FYVCRR5.js:3:4373
    at Ua (main-6FYVCRR5.js:3:2222)
    at i.subscribe (main-6FYVCRR5.js:3:4289)
    at e.<anonymous> (main-6FYVCRR5.js:18:11341)
    at Generator.next (<anonymous>)
    at chunk-2WQGNY7Y.js:1:1640
    at new t (polyfills-LZBJRJJE.js:2:2128)

 this is the compiled source which I can see in devtools

            getEventSource(t) {
            return new (void 0)(t,{
                headers: {
                    Authorization: "Bearer " + this.token
                },
                retry: 3e3
            })
        }

    here's my source code 

import { Injectable, NgZone, inject } from '@angular/core';
import { Observable } from 'rxjs';
import { apiUrl } from '../../environment';
import { AuthRegularService } from '../services/auth-regular.service';
import { EventSource as CustomEventSource } from 'extended-eventsource';

@Injectable({
 providedIn: 'root',
})
export class SseService {
 token = inject(AuthRegularService).getToken();
 constructor(private _zone: NgZone) {}
 getServerSentEvent(url: string): Observable<any> {
   return Observable.create((observer: any) => {
     const eventSource = this.getEventSource(url);
     eventSource.onmessage = (event) => {
       this._zone.run(() => {
         // console.log("SSE event data received: ", event.data)
         if (!event.data) {
           console.log('False data received', event.data);
           // do not forward as this causes an error, "", false, undefined, null
         } else if (JSON.parse(event.data).msg === 'PROCESS_ENDED') {
           eventSource.close();
           observer.next(event);
         } else {
           observer.next(event);
         }
       });
     };
     eventSource.onerror = (error: any) => {
       console.log('Getting server sent event error:', error);
       eventSource.close();
       return;
       // this._zone.run(() => {
       //   observer.error(error);
       // });
     };
   });
 }

 private getEventSource(url: string): EventSource {
   return new CustomEventSource(url, {
     headers: {
       Authorization: 'Bearer ' + this.token,
     },
     retry: 3000,
   });
 }
}

In several places this package uses console methods to write directly to standard output. This can be problematic when used from a CLI program where I want to have full control over my program's output. Currently I'm seeing messages like Connection established in my output which I have no straightforward way of preventing.

Would you consider accepting a pull request which removes all usages of console.*? Or if not, perhaps a new option to allow some mechanism to disable them?

How would I extract an 401 from the event in onerror?

I can do this:

eventSource.addEventListener('specific-event-type', msg => { ... });

And it'll fire, but

eventSource.onmessage = msg => { .... }

Will never fire.