compose

compose1.js

function fn1(num) {
  console.log('fn1', num)
  return num
}

function fn2(num) {
  console.log('fn2', num)
  return num
}

function fn3(num) {
  console.log('fn3', num)
  return num
}

function fn4(num) {
  console.log('fn4', num)
  return num
}

function compose(funs) {
  // 返回的 composed， 必然是一个参数为 num 的函数
  return (num) => funs.reduce((previous, current) => current(previous), num)
}

let composed = compose([fn1, fn2, fn3, fn4])

composed(1)

compose2.js

function fn1(next){
    console.log('fn1')
    next()
    console.log('end fn1')
}

function fn2(next){
    console.log('fn2')
    next()
    console.log('end fn2')
}

function fn3(next){
    console.log('fn3')
    next()
    console.log('end fn3')
}

function fn4(next){
    console.log('fn4')
    next()
    console.log('end fn4')
}

function compose(funs) {
  return oNext => funs.reduceRight((previous, current) => () => current(previous), oNext)()
}


let composed = compose([fn1, fn2, fn3, fn4])

composed(() => console.log('oNext called'))