Getting started
1. Installing
2. Hello world example
3. Express application generator
4. Basic routing
5. Serving static files in Express
6. FAQ
Guide
1. Routing
2. Writing middleware for use in Express apps
3. Using middleware
4. Using template engines with Express
5. Error handling
6. Debugging Express
7. Express behind proxies
8. Moving to Express 4
9. Moving to Express 5
10. Database integration
Advanced topics
1. Developing template engines for Express
2. Process managers for Express apps
3. Security updates
4. Production Best Practices: Security
5. Production best practices: performance and reliability
API
API
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Figuren
Express在内部使用调试模块记录有关路由匹配，正在使用的中间件功能，应用程序模式以及请求 - 响应周期流的信息。
debug就像增强版本console.log，但不像console.log你不必编写debug代码中注释日志。日志记录默认情况下处于关闭状态，可以通过使用DEBUG环境变量有条件地启用。
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
在Windows上，使用相应的命令。
> set DEBUG=express:* & node index.js
在由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
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
仅查看来自路由器实施的日志，请将DEBUG值设置为express:router。同样，要仅从应用程序实现中查看日志，请将DEBUG值设置为express:application，等等。
express生成的应用程序
由express命令生成的应用程序也使用debug模块，其调试名称空间的作用域为应用程序的名称。
例如，如果您生成了应用程序$ express sample-app，则可以使用以下命令启用调试语句：
$ DEBUG=sample-app node ./bin/www
您可以通过指定逗号分隔的名称列表来指定多个调试名称空间：
$ DEBUG=http,mail,express:* node index.js
有关更多信息debug，请参阅调试。