JS Middleware class in 8 lines

middleware.js

class Middleware{
  constructor(){ this.m = [] }
  use(fn){ this.m.push(fn) }
  run(d, f){ this._execute(d, f) }
  _execute(d, f){ this.m.reduceRight((n, c) => v => c(v, n), f)(d) }
}

// usage
const m = new Middleware();

// append middlewares
m.use(function(data, next){
  next(data + 1)
})

m.use(function(data, next){
  next(data + 1)
})

m.use(function(data, next){
  next(data + 1)
})

// execute
// first argument – data
// second argument – finish function, will
// recieve result after all middlewares
m.run(1, function(result){
  console.log(result) //=> 4
})

// to iterrupt middlewares chain just don't call next()
// you can test it out by playing with this code above