[Bug]: cannot extend winston.logger

🔎 Search Terms

class extend, extend logger

The problem

TypeError: Class extends value undefined is not a constructor or null

What version of Winston presents the issue?

v3.8.1

What version of Node are you using?

v16.16.0

If this worked in a previous version of Winston, which was it?

No response

Minimum Working Example

import * as winston from 'winston'

class LogService extends winston.Logger {
  private static instance: LogService

  constructor () {
    super({
      level: process.env.LOG_LEVEL ?? 'info',
      exitOnError: false,
      format: winston.format.combine(winston.format.timestamp(), winston.format.json()),
    })
  }

  static getInstance = (): LogService => {
    if (LogService.instance == null) { LogService.instance = new LogService() }
    return LogService.instance
  }
}

export default LogService

[jianzhou520]

same issue

[ludgerey]

Having a similar issue with Transport. Is this related?

class WinstonEventEmitterTransport extends Transport {
                                           ^
TypeError: Class extends value undefined is not a constructor or null

Not sure if I’ve understood correctly but I am able to extend from Transport class using the 'winston-transport' module.

I got my specific problem fixed by by setting "esModuleInterop": true" in tsconfig.json. Sorry for the late update.