1. Middleware.prototype.use = function(fn){
    2.   if(typeof fn !== 'function'){
    3.     throw 'middleware must be a function';
    4.   }
    5.   this.cache.push(fn);
    6.   return this;
    7. }
    9. Middleware.prototype.next = function(fn){
    10.   if(this.middlewares && this.middlewares.length > 0 ){
    11.     var ware = this.middlewares.shift();
    12.     ware.call(this, this.next.bind(this));
    13.   }
    14. }
    15. Middleware.prototype.handleRequest = function(){//执行请求
    16.   this.middlewares = this.cache.map(function(fn){//复制
    17.     return fn;
    18.   });
    19.   this.next();
    20. }