compose

function compose(...fns) {
  return fns.reduce((prev, next) => {
    return (...args) => {
      return next(prev(...args))
    }
  })
}

测试代码

// // 用法如下:
function fn1(x) {
  return x + 1
}
function fn2(x) {
  return x + 2
}
function fn3(x) {
  return x + 3
}
function fn4(x) {
  return x + 4
}
const a = compose(fn1, fn2, fn3, fn4)
console.log(a(1))