June 2021
Intermediate to advanced
290 pages
9h 21m
Chinese
Content preview from Node与Express开发（第2版）
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116
｜
第
12
章
const port = process.env.PORT || 3000
app.listen(port, () => console.log(`Express started in ` +
`${app.get('env')} mode at http://localhost:${port}` +
`; press Ctrl-C to terminate.`))
如果你现在启动应用，就会看到它正在开发模式下运行，这是默认模式。尝试一下让它在
生产模式下运行：
$ export NODE_ENV=production
$ node meadowlark.js
如果使用
Unix/BSD
，就有一种便捷的写法，可以让你仅在这个命令的运行期间修改环境：
$ NODE_ENV=production node meadowlark.js
这会让服务器仅在生产模式下运行，当服务器终止时，
NODE_ENV
环境变量将不会被修改。
我特别喜欢这种便捷的写法，它降低了偶然误设环境变量的可能性，毕竟误设的值未必需
要全部应用。
如果你以生产模式启动
Express
，可能会出现一些警告，提示有些组件不适
用于生产模式。如果你是跟着本书示例操作的，就会发现
connect.session
使用的是内存存储，不适用于生产环境。等到第
13
章我们把它切换为数据
库存储后，这条警告就会消失。
12.2
特定环境的配置
虽然单独修改运行环境好像没有太大作用，但是在生产模式下，
Express
会打印更多的警
告信息（比如通知你某些模块已经淘汰了 ...
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I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.