调试 Express

¥Debugging Express

要查看 Express 中使用的所有内部日志，请在启动应用时将 DEBUG 环境变量设置为 express:*。

¥To see all the internal logs used in Express, set the DEBUG environment variable to express:* when launching your app.

$ DEBUG=express:* node index.js

在 Windows 上，使用相应的命令。

¥On Windows, use the corresponding command.

> set DEBUG=express:* & node index.js

在 express 生成器 生成的默认应用上运行此命令会打印以下输出：

¥Running this command on the default app generated by the express generator prints the following 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

当向应用发出请求时，你将看到 Express 代码中指定的日志：

¥When a request is then made to the app, you will see the logs specified in the Express code:

  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

要仅查看来自路由实现的日志，请将 DEBUG 的值设置为 express:router。同样，要仅从应用实现中查看日志，请将 DEBUG 的值设置为 express:application，依此类推。

¥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.

express 生成的应用

¥Applications generated by express

由 express 命令生成的应用使用 debug 模块，其调试命名空间的范围为应用的名称。

¥An application generated by the express command uses the debug module and its debug namespace is scoped to the name of the application.

例如，如果你使用 $ express sample-app 生成应用，则可以使用以下命令启用调试语句：

¥For example, if you generated the app with $ express sample-app, you can enable the debug statements with the following command:

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

你可以通过分配以逗号分隔的名称列表来指定多个调试命名空间：

¥You can specify more than one debug namespace by assigning a comma-separated list of names:

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

高级选项

¥Advanced options

通过 Node.js 运行时，你可以设置一些环境变量来改变调试日志的行为：

¥When running through Node.js, you can set a few environment variables that will change the behavior of the debug logging:

名称	目的
DEBUG	启用/禁用特定的调试命名空间。
DEBUG_COLORS	是否在调试输出中使用颜色。
DEBUG_DEPTH	对象检查深度。
DEBUG_FD	要将调试输出写入的文件描述符。
DEBUG_SHOW_HIDDEN	显示检查对象的隐藏属性。

注意：以 DEBUG_ 开头的环境变量最终会转换为与 %o/%O 格式化程序一起使用的选项对象。有关完整列表，请参阅 util.inspect() 的 Node.js 文档。

¥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.