How does .use (middleware handler) work?

Question

JavaScript

Already in several libraries, I discovered the ability to embed middleware, and I became interested in how this function works from the inside .use
Therefore, I decided to ask a question here.
So, how does .use - the middleware handler - work from the inside? Can I have examples of the source code of .use (sorry, I googled superficially, I didn’t find it)?

Answer 1

here, I wrote my express with middleware

class Express {
  response = {}
  middles = []

  use = func => this.middles.push(func)

  get = () => {
    this.middles.forEach(func => func(this.response))
    console.log('RESPONSE NOW: ',this.response)
  }
}

app = new Express()
app.get()
// response: {}

function addBla(res) { res.bla = 17 }
// миддлвар добавляет какое-то свойство в response от сервера

app.use(addBla)
app.get()
// response: {bla: 17}

Answer 2

Under the hood, all kinds of express use https://www.npmjs.com/package/connect , and he already drives everything

Answer 3

app.use
router.use