用js徒手写一个中间键

• 2020 年 2 月 18 日
• 筆記

什么是中间键？ 下图中 C和D 的部分就是中间键

创建一个js文件 middleware.js 内容如下

const App = () => {    const req = {      type: 'request',      params: []    }    const res = {      type: 'response'    }      const middlewares = []    const use = fn => middlewares.push(fn)      const runMiddlewares = index => {      const count = middlewares.length      if (index < count)        middlewares[index].apply(null, [req, res, () => runMiddlewares(index + 1)])    }      const get = (path, fn) => {      runMiddlewares(0)      fn.apply(null, [res, res])    }      return {      get,      use    }  }    const app = App()  app.use((req, res, next) => {    req.params.id = 5;    console.log(req, 'request object accessed from middleware 1')    console.log('Middleware 1')    next()  })  app.use((req, res, next) => {    console.log('Middleware 2')    next()  })      app.use((req, res, next) => {    console.log('Middleware 3')    next()  })    app.get('/', (req, res) => {    console.log('Response object accessd from get function')  })

执行这段代码

node middleware.js