Debug di Express
Per visualizzare tutti i log interni utilizzati in Express, impostare la variabile di ambiente DEBUG su express:* quando si avvia l’applicazione.
$ DEBUG=express:* node index.js Su Windows, utilizzare il comando corrispondente.
> $env:DEBUG = "express:*"; node index.js L’esecuzione di questo comando sull’applicazione predefinita generata da Programma di creazione express consentirà di stampare il seguente output:
$ DEBUG=express:* node ./bin/www express:router:route new / +0ms express:router:layer new / +1ms express:router:route get / +1ms express:router:layer new / +0ms express:router:route new / +1ms express:router:layer new / +0ms express:router:route get / +0ms express:router:layer new / +0ms express:application compile etag weak +1ms express:application compile query parser extended +0ms express:application compile trust proxy false +0ms express:application booting in development mode +1ms express:router use / query +0ms express:router:layer new / +0ms express:router use / expressInit +0ms express:router:layer new / +0ms express:router use / favicon +1ms express:router:layer new / +0ms express:router use / logger +0ms express:router:layer new / +0ms express:router use / jsonParser +0ms express:router:layer new / +1ms express:router use / urlencodedParser +0ms express:router:layer new / +0ms express:router use / cookieParser +0ms express:router:layer new / +0ms express:router use / stylus +90ms express:router:layer new / +0ms express:router use / serveStatic +0ms express:router:layer new / +0ms express:router use / router +0ms express:router:layer new / +1ms express:router use /users router +0ms express:router:layer new /users +0ms express:router use / <anonymous> +0ms express:router:layer new / +0ms express:router use / <anonymous> +0ms express:router:layer new / +0ms express:router use / <anonymous> +0ms express:router:layer new / +0ms Quando successivamente viene effettuata una richiesta all’applicazione, verranno visualizzati i log specificati nel codice Express:
express:router dispatching GET / +4h express:router query : / +2ms express:router expressInit : / +0ms express:router favicon : / +0ms express:router logger : / +1ms express:router jsonParser : / +0ms express:router urlencodedParser : / +1ms express:router cookieParser : / +0ms express:router stylus : / +0ms express:router serveStatic : / +2ms express:router router : / +2ms express:router dispatching GET / +1ms express:view lookup "index.pug" +338ms express:view stat "/projects/example/views/index.pug" +0ms express:view render "/projects/example/views/index.pug" +1ms Per visualizzare i log solo dall’implementazione router impostare il valore DEBUG su express:router. In modo simile, per visualizzare i log solo dall’implementazione dell’applicazione impostare il valore DEBUG su express:application e così via.
Applicazioni generate da express
Un’applicazione generata dal comando express utilizza inoltre il modulo debug e il relativo spazio dei nomi di debug viene associato al nome dell’applicazione.
Ad esempio, se l’applicazione è stata generata con $ express sample-app, è possibile abilitare le istruzioni di debug con il seguente comando:
$ DEBUG=sample-app:* node ./bin/www È possibile specificare più di uno spazio dei nomi di debug assegnando un elenco di nomi separati da virgola:
$ DEBUG=http,mail,express:* node index.js Advanced options
When running through Node.js, you can set a few environment variables that will change the behavior of the debug logging:
| Name | Purpose |
|---|---|
DEBUG | Enables/disables specific debugging namespaces. |
DEBUG_COLORS | Whether or not to use colors in the debug output. |
DEBUG_DEPTH | Object inspection depth. |
DEBUG_FD | File descriptor to write debug output to. |
DEBUG_SHOW_HIDDEN | Shows hidden properties on inspected objects. |
Note
The environment variables beginning with DEBUG_ end up being converted into an Options object that gets used with %o/%O formatters. See the Node.js documentation for util.inspect() for the complete list.