LoggerService is used in YABF but you can also ise it.

As LoggerService is a service provided by YABF, you don't have to register it with the provide method. You can use it as dependency of your service or controller.

For a controller:

const app = WebApplication.createInstance()
app.declare(YourController, [LoggerService])

// ...

class YourController extends Controller {
  constructor(private loggerService: LoggerService) {
    super()
  }
}

For a service:

const app = WebApplication.createInstance()
app.provide(YourService, [LoggerService])

// ...

class YourService {
  constructor(private loggerService: LoggerService) {}
}

Of course, this method works also for the other children of AbstractApplication.

LoggerService use scope to display messages. A scope regroup all the information about a group of messages.

A scope is identified thank to its unique namespace. LoggerService display the namespace in front of each message it writes.

A namespace should respect the following exemples' format:

• yabf
• yabf:router
• http:v2
• js:local-storage

The : separator works like an ancestor/child delimitator.

LoggerService may work with other namespace formats but we build and test it with this one and we can't guarantee the other will work too.

Namespaces are filterable.

LoggerService is compatible with the debug npm package used by other project like ExpressJs. You have to use the same environment variable to activate log messages.

By default this variable doesn't exist, so no messages are shown. Set it to '*' to show all message.

export $DEBUG=*

Sometimes you don't want to overwelmed yourself with all the log messages of your application. Namespaces are filterable.

To display messages from a specific part of your application, use its specific namespace as a filter:

export $DEBUG=yabf:router

To display messages from a specific part of your application and its children, use a wildcard (*) in the filter:

export $DEBUG=yabf:router:*

To display messages from several specific parts of your application, use several namespace filters separated by a coma (,):

export $DEBUG=yabf:router:*,yabf:controller

To hide messages from a specific part of your application, use the negative indicator (-) in filter:

export $DEBUG=*,-yabf:controller

Be aware that the negative filters will always considered as priority filters. The following example work the exact same way than the one above.

export $DEBUG=-yabf:controller,*

In JS:

const app = WebApplication.createInstance()
app.declare(YourController, [YourService, LoggerService])
app.provide(YourService, [LoggerService])

// ...

class YourController extends Controller {
  constructor(private yourService: YourService, private loggerService: LoggerService) {
    super()

    const log = this.loggerService.registerScope('your-app:your-controller')

    log('Controller successfully started')
  }
}

// ...

class YourService {
  constructor(private loggerService: LoggerService) {
    this.loggerService.registerScope('your-app:your-service')
  }

  action(path: string) {
    // ...
    this.loggerService.log('your-app:your-service', `New path ("${path}") processed in action`)
  }
}

In Bash:

$ DEBUG=* node ./your-app.js
yabf:router GET / +0ms
your-app:your-service New path ("/") processed in action +0ms
your-app:your-controller Controller successfully started +0ms
your-app:your-service New path ("/") processed in action +10ms

or

$ DEBUG=*,-your-app:your-service:* node ./your-app.js
yabf:router GET / +0ms
your-app:your-controller Controller successfully started +0ms