simple express-like middleware

middleware.js

class Middleware {
  constructor () {
    this.stack = []
  }

  use (fn) {
    this.stack.push(fn)
  }

  go (next, remaining = this.stack.slice()) {
    const fn = remaining.shift()
    if (fn) {
      fn(() => this.go(next, remaining))
    } else {
      next()
    }
  }
}

// Usage

const app = new Middleware()
app.use(function (next) {
  console.log(1)
  setTimeout(function () {
    next()
  }, 100)
})

app.use(function (next) {
  console.log(2)
  setTimeout(function () {
    next()
  }, 100)
})

app.go(function () {
  console.log('done')
})