Debugging Express调试Express

To see all the internal logs used in Express, set the DEBUG environment variable to express:* when launching your app.要查看Express中使用的所有内部日志，请在启动应用程序时将DEBUG环境变量设置为Express:*。

$ DEBUG=express:* node index.js

On Windows, use the corresponding command.在Windows上，使用相应的命令。

> $env:DEBUG = "express:*"; node index.js

Running this command on the default app generated by the express generator prints the following output:在express生成器生成的默认应用程序上运行此命令会打印以下输出：

$ 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

When a request is then made to the app, you will see the logs specified in the Express code:当向应用程序发出请求时，您将看到Express代码中指定的日志：

  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

To see the logs only from the router implementation, set the value of DEBUG to express:router. Likewise, to see logs only from the application implementation, set the value of DEBUG to express:application, and so on.要只查看路由器实现的日志，请将DEBUG的值设置为express:router。同样，要只查看应用程序实现的日志，请将DEBUG的值设置为express:application，依此类推。

Applications generated by expressexpress生成的应用程序

An application generated by the express command uses the debug module and its debug namespace is scoped to the name of the application.express命令生成的应用程序使用debug模块，其调试命名空间的范围为应用程序的名称。

For example, if you generated the app with $ express sample-app, you can enable the debug statements with the following command:例如，如果您使用$ express sample-app生成了应用程序，则可以使用以下命令启用调试语句：

$ DEBUG=sample-app:* node ./bin/www

You can specify more than one debug namespace by assigning a comma-separated list of names:您可以通过分配逗号分隔的名称列表来指定多个调试命名空间：

$ DEBUG=http,mail,express:* node index.js

Advanced options高级选项

When running through Node.js, you can set a few environment variables that will change the behavior of the debug logging:在运行Node.js时，您可以设置一些环境变量来改变调试日志的行为：

Name名字 Purpose目的
DEBUG Enables/disables specific debugging namespaces.启用/禁用特定的调试命名空间。
DEBUG_COLORS Whether or not to use colors in the debug output.是否在调试输出中使用颜色。
DEBUG_DEPTH Object inspection depth.物体检查深度。
DEBUG_FD File descriptor to write debug output to.用于写入调试输出的文件描述符。
DEBUG_SHOW_HIDDEN Shows hidden properties on inspected objects.显示被检查对象的隐藏属性。

Note备注

The environment variables beginning with DEBUG_ end up being converted into an Options object that gets used with %o/%O formatters.以DEBUG_开头的环境变量最终被转换为Options对象，该对象与%o/%O格式化程序一起使用。 See the Node.js documentation for util.inspect() for the complete list.有关完整列表，请参阅Node.js文档中的util.inspect()。