process 是node应用与用户环境的桥梁，process.env则为用户环境的拷贝。我们可以通过process设置port以及各种环境配置，但在生产中不建议这样做。我们应该设置一个配置文件专门用于环境的各种配置，然后再const config = require('xxxx/config')进来进行配置。
process是EventEmiter的一个实例。所以你可以emit事件以及监听事件。
process.on(exit, code => {
// 在process停止之前，这里可以做最后的sync操作
console.log(`exit with ${code}`)
})
当event loop无事可做或者当你手动执行process.exit的时候exit事件会触发
process.on('uncaughtException', err => {
// js exception is not handle
// do any cleanup and exit anyway
console.error(err) // do not do just that
// FORCE exit the process too
process.exit(1)
})
// keep the event loop busy
proces.stdin.resume()
// trigger a typeError exception
console.dog()
BUFFER
```
const { StringDecoder } = require('string_decoder')
const decoder = new StringDecoder('utf8')
process.stdin.on('readable', () => {
const chunk = process.stdin.read()
if (chunk != null) {
const buffer = Buffer.from([chunk])
console.log('with toString():', buffer.toString())
// if you are receiving bytes as chunk in a stream. you should always use String Decoder
console.log('with StringDecoder:', decoder.write(buffer) )
}
})
```
