🌐 Nodejs.cn

调试 Express

要查看 Express 中使用的所有内部日志，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.

Terminal window
$ DEBUG=express:* node index.js

在 Windows 上，使用相应的命令。

🌐 On Windows, use the corresponding command.

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

在默认由 express generator 生成的应用上运行此命令会打印出以下输出：

🌐 Running this command on the default app generated by the express generator prints the following output:

Terminal window
$ 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

当然后向应用发出请求时，你将看到在 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:

Terminal window
  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，要仅查看来自应用实现的日志，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，其调试命名空间的作用域限于应用的名称。

🌐 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 生成了应用，你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:

Terminal window
$ 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:

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

高级选项

🌐 Advanced options

在通过 Node.js 运行时，你可以设置一些环境变量，这些变量将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对象检查的深度。
DEBUG_FD写入调试输出的文件描述符。
DEBUG_SHOW_HIDDEN显示被检查对象的隐藏属性。

Note

以 DEBUG_ 开头的环境变量最终会被转换为一个 Options 对象，该对象会与 %o/%O 格式化器一起使用。完整列表请参阅 Node.js 文档中的 util.inspect()。

🌐 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.