为何一定要加return？ return result;这句指的是返回result值？

<script>

        var obj1={

            a:1,

            b:2,

            c:[33,44,{

                m:55,

                n:66,

                p:[77,88]

            }]

        };

               //新参o就是对象obj1里的元素

             function deepClone(o){

                 if(Array.isArray(o)){

                     var result=[];

                     for(var i=0;i<o.length;i++){

                         result.push(deepClone(o[i]));

                     }

                 } else if(typeof o=="object"){

                     var result={};

                     for(var k in o){

                        result[k]=deepClone(o[k]);

                     }

                 }

                 else{var result=o;}

                 //??

                 return result;

             }

             var obj2=deepClone(obj1);

             console.log(obj2);

    </script>