为何一定要加return？不加return得不到递归前push的值是什么意思啊？

  <script>

        var obj1={

            a:1,

            b:2,

            c:[33,44,{

                m:55,

                n:66,

                p:[77,88]

            }]

        };

             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;}

                 //为何一定要加return？不加return得不到递归前push的值是什么意思啊？

                 return result;

             }

             var obj2=deepClone(obj1);

             console.log(obj2);

    </script>