1. 简化版

      1. function compose(middleware) {
      2.  return function() {
      3.  function dispatch(i) {
      4.      let fn = middleware[i]
      5.    if (!fn) return
      6.    return fn(function next()) {
      7.        return dispatch(i + 1)          
      8.          }
      9.  }
      10.    return dispatch(0)
      11. }
      12. }

    2. Promise 版

    1. function compose(middleware) {
    2.     return function(ctx) {
    3.     return dispatch(0)
    4.       function dispatch(i) {
    5.         let fn = middleware[i]
    6.             if (!fn) return Promise.resolve()
    7.       return Promise.resolve(
    8.         fn(function next() {
    9.               return dispatch(i + 1)
    10.           })
    11.       )
    12.     }
    13.   }
    14. }