In node express with socket.io, why does my Content-Type header not include a charset value when loading the socket.io.js file? #4589

owntheweb · 2023-01-10T17:15:54Z

owntheweb
Jan 10, 2023

(Also posted here for internet points)

Hello socket.io gurus,

I have a node express server setup with socket.io. I had a question come up about why charset wasn't being set to UTF-8 in my response header when loading socket.io.js from my client-side html page. If I were to load it in the socket.io demo page, I see the expected charset:

content-type: application/javascript; charset=utf-8

In my app however, I see:

content-type: application/javascript;

(note: I need to do a hard refresh to see these headers show up in dev tools otherwise I just get a 304 no change)

Everything else in the app returns the charset header of UTF-8, so this leaves me scratching my head. Here's the minimal version of the app that can reproduce the issue:

help.ts

import * as http from 'http'
import express, { Application, Request, Response } from 'express'
import cors from 'cors'
import { Server } from 'socket.io'

let server

const startExpress = (): Promise<http.Server> => {
  return new Promise((resolve, reject) => {
    const app = express()
    app.use(cors())
    const port = Number(process.env.PORT || 3000)

    const server = app
      .listen(port, () => {
        setRoutes(app)
        resolve(server)
      })
      .on('error', (error: Error) => {
        reject(error)
      })
  })
}

const setRoutes = (app: Application) => {
  app.get('/hi', (request: Request, response: Response) => {
    response.sendFile(__dirname + '/hi.html')
  })
}

const setupSocketIoServer = (expressServer: http.Server): void => {
  server = new Server(expressServer, { cors: { origin: '*' } })
  // add events and such, not needed for this demo
}

const go = async () => {
  // start app
  const expressServer = await startExpress()

  // start socket.io
  setupSocketIoServer(expressServer)
}

go()

hi.html

<!DOCTYPE html>
<html>
  <head>
    <title>Hello</title>
    <script src="/socket.io/socket.io.js"></script>
  </head>
  <body>
    <h1>Hello</h1>
  </body>
</html>

Getting it started:

npx ts-node help.ts

Since this is a module-provided file, I cannot seem to override it with something like:

app.use((req, res, next) => {
  if (/.*\.js/.test(req.path)) {
    res.charset = 'utf-8'
  }
  next()
})

"express": "^4.18.2",
"socket.io": "^4.5.4"

I'm stumped. Any idea of what I might be missing?

Answered by darrachequesne

Jan 16, 2023

Hi! The charset isn't currently included when serving the client bundle:

socket.io/lib/index.ts

Lines 567 to 570 in 54d5ee0

     res.setHeader(  
   "Content-Type",  
   "application/" + (isMap ? "json" : "javascript")  
   );  

 

I guess it's automatically in the chat demo (coming from https://cdnjs.cloudflare.com/ajax/libs/socket.io/2.3.0/socket.io.js).

View full answer

darrachequesne · 2023-01-16T07:04:33Z

darrachequesne
Jan 16, 2023
Maintainer

Hi! The charset isn't currently included when serving the client bundle:

socket.io/lib/index.ts

Lines 567 to 570 in 54d5ee0

    
           res.setHeader( 
        
             "Content-Type", 
        
             "application/" + (isMap ? "json" : "javascript") 
        
           );

I guess it's automatically in the chat demo (coming from https://cdnjs.cloudflare.com/ajax/libs/socket.io/2.3.0/socket.io.js).

4 replies

owntheweb Jan 24, 2023
Author

Thank you!

darrachequesne Jan 24, 2023
Maintainer

@ChrisAtBombBomb this will be fixed in next release: 93d446a

qiulang Jan 31, 2023

@darrachequesne RFC 9239 Updates to ECMAScript Media Types, which was published in May 2022, the Encoding section says

Module goal sources MUST be encoded as UTF-8; all other encodings will fail. Source goal sources SHOULD be encoded as UTF-8

So does it really necessary to set UTF-8 in source code ?

darrachequesne Feb 8, 2023
Maintainer

@qiulang I guess it doesn't hurt to set an explicit charset.

@ChrisAtBombBomb 93d446a was included in version 4.6.0 🚀

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	res.setHeader(
	"Content-Type",
	"application/" + (isMap ? "json" : "javascript")
	);

In node express with socket.io, why does my Content-Type header not include a charset value when loading the socket.io.js file? #4589

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owntheweb Jan 10, 2023

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