Brief explanation of redux middleware's work internals

compose.js

function compose(...funcs) {
  if (funcs.length === 0) {
    return arg => arg
  }

  if (funcs.length === 1) {
    return funcs[0]
  }

  return funcs.reduce((a, b) => (...args) => a(b(...args)));
}

const a = (cb) => {
	console.log('this is a first cycle');
	return () => {
		console.log('a result');
		return cb();
	};
}

const b = (cb) => {
	console.log('this is b first cycle');
	return () => {
		console.log('b result');
		return cb();
	};
}

const c = (cb) => {
	console.log('this is c first cycle');
	return () => {
		console.log('c result');
		return cb();
	};
}

console.log('---');

compose(a,b,c)(()=>{})();