frmwrk.js

frmwrk.js

// Makes a sync middleware
const make = (name) => {
  return (ctx, next) => {
    ctx.calls = ctx.calls || 0
    ctx.calls += 1;
    console.log(`Doing ${name} PRE`);
    return next(ctx);
  }
}

// makes an async middleware
const makeAsync = (name) => {
  return async (ctx, next) => {
    console.log(`Doing ${name} PRE`);
    const r = await next(ctx);
    console.log(`Doing ${name} POST`, r);
    return { ...r, name };
  }
}

// Processes a handler with middlewares, in an out
function use(middlewares, handler, ctx = {}) {
  const [m, ...rest] = middlewares;
  if (!m) {
    return handler(ctx);
  }
  return m(ctx, (uCtx) => {
    return use(rest, handler, uCtx || ctx);
  });
}

// Make 4 middlewares
const a = make('1');
const b = makeAsync('2');
const c = make('3');
const d = makeAsync('4');

use([
  a, b, c, d 
], async (ctx) => {
  console.log('Doing route... ');
  return { a: 1, b: 2, calls: ctx.calls };
})

out

Doing 1 PRE
Doing 2 PRE
Doing 3 PRE
Doing 4 PRE
Doing route... 
Doing 4 POST { a: 1, b: 2, calls: 2 }
Doing 2 POST { a: 1, b: 2, calls: 2, name: '4' }