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A very minimal Javascript (ES5 & ES6) Middleware Pattern Implementation
class Middleware {
constructor() {
// Array prototype last
if (!Array.prototype.last) {
Array.prototype.last = function() {
return this[this.length - 1];
}
}
// Array prototype reduceOneRight
if (!Array.prototype.reduceOneRight) {
Array.prototype.reduceOneRight = function() {
return this.slice(0, -1);
}
}
}
use(fn) {
this.go = ((stack) => (...args) => stack(...args.reduceOneRight(), () => {
let _next = args.last();
fn.apply(this, [...args.reduceOneRight(), _next.bind.apply(_next, [null, ...args.reduceOneRight()])]);
}))(this.go);
}
go(...args) {
let _next = args.last();
_next.apply(this, args.reduceOneRight());
}
}
var middleware = new Middleware();
middleware.use((hook, next) => {
setTimeout(() => {
hook.value++;
next();
}, 10);
});
middleware.use((hook, next) => {
setTimeout(() => {
hook.value++;
next();
}, 10);
});
var start = new Date();
middleware.go({value:1}, (hook) => {
console.log(hook.value); // 3
console.log(new Date() - start); // around 20
});
@swapnilaryan

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@swapnilaryan swapnilaryan commented Sep 18, 2018

Hi,
Great job in simplifying the implementation of darrenscerri/Middleware.js
Can you simplify more the "use" method and "next()" functionality as I am new to ES6 and JS world ?

@coreybutler

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@coreybutler coreybutler commented Feb 15, 2020

Modifying the array prototype seems unnecessary, with potential consequences. This version accomplishes the same thing.

const last = a => a[a.length - 1]
const reduce = a => a.slice(0, -1)

class Middleware {
  use (method) {
    this.go = ((stack) => (...args) => stack(...reduce(args), () => {
      const next = last(args)
      method.apply(this, [...reduce(args), next.bind.apply(next, [null, ...reduce(args)])])
    }))(this.go)
  }

  go (...args) {
    last(args).apply(this, reduce(args))
  }
}
@shennan

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@shennan shennan commented May 16, 2020

In order to chain a lá

middleware
  .use(fn)
  .use(fn)

you could return this at the end of the use method.

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