为什么不弹出cc呢

Question

javascript

Answer 1

function add(obj,types,fns){
            if(typeof obj[types]!="function"){
                obj[types]=fns;
                
                }
            else{
                
                var old=obj[types];
                
                obj[types]=function  (){
                    old();
                    fns();
                    
                    }
                
                }   
                
            
            }
        add(bTn,"onclick",function(){
            
            alert("cc");
            })