源代码在这里

Part 1. HelloWorld

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const http = require("http")
const host = process.env.HOST || "localhost"
const port = process.env.PORT || 3000

/**
 * 用于处理请求的函数
 */
const requestHandler = (req, res) => {
  res.statusCode = 200
  res.setHeader("Content-Type", "text/plain")
  res.end("Hello World")
}

// 创建 server
const server = http.createServer(requestHandler)

// 开启监听
server.listen(port, host, (err) => {
  if (err) {
    return console.log("something bad happened", err)
  }

  console.log(`server is listening on ${host}:${port}`)
})

Part 2. ContentType: JSON

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const requestHandler = (req, res) => {
  res.statusCode = 200
  res.setHeader("Content-Type", "application/json")
  res.end(JSON.stringify({ message: "Hello World" }))
}

JSON 返回意味着有一个 Content-Type Header 和对应的 JSON 文本 body

Part 3. Router

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const requestHandler = (req, res) => {
  res.statusCode = 200
  switch (req.url) {
    case "/json": {
      jsonHandler(req, res)
      break
    }
    default: {
      defaultHandler(req, res)
      break
    }
  }
}

可以通过 req.url 判定来源 url 以此提供路由功能