Redux中间件applyMiddleware核心思想

　　　　 function a(next){
            return function(action){
                // console.log(next); //这里的next为b函数的返回值
                action = action + 1;  
                next(action);
            }
        }    

        function b(next){
            return function(action){
                // console.log(next);//这里next为初始的dispatch
                action = action + 1;
                next(action);
            }
        }    

        let arr  = [];
        arr.push(a);
        arr.push(b);

        let compose = arr.reduce(function(prev,curr){
            return function(next){
                    return prev(curr(next))
            }
        });

        var globalV = 0; //定义一个全局变量,用来计数

        //初始的dispatch
        let dispatch = function(action){
            //初始功能
            globalV += action;
        }
        //加强后的dispatch 
        let strendispatch = compose(dispatch);

        strendispatch(1);

        console.log(globalV); //结果是  3