A variety of methods to realize function composition

// Responsibility chain model (execute one after another)

const fn1 = (x, y) => x + y;
const fn2 = (z) => z * z;
Copy the code

// Normal combination

const compose = (fn1, ... other) => (... args) => { let ret = fn1(... args); other.forEach(item => { ret = item(ret); }); return ret; }Copy the code

// Redux middleware combination

const reduxCompose = (... fns) => fns.reduce((a, b) => (... args) => b(a(... args))) const fn = reduxCompose(fn1, fn2); console.log(fn(1, 2));Copy the code

// The onion circle model (half-and-half execution)

const koaCompose = (middlewares) => { return function () { return dispatch(0); function dispatch(idx) { const fn = middlewares[idx]; if (! fn) { return Promise.resolve(); } return Promise.resolve( fn(function next() { return dispatch(idx + 1) }) ) } } }; async function func1(next) { console.log("func1"); await next(); console.log("func1 end"); } async function func2(next) { console.log("func2"); await delay(); await next(); console.log("func2 end"); } async function func3(next) { console.log("func3"); } async function delay() { return new Promise((resolve, reject) => { setTimeout(() => { resolve(); }, 2000); }) } const middlewares = [func1, func2, func3]; const finaFn = koaCompose(middlewares); finaFn()Copy the code