js原型链函数覆盖问题

Question

同一个原型链函数，传入不同参数，得出不同的结果，但后一个函数覆盖了前一个函数，两个函数输出相同的结果，此为排序的示例，排序优先级为age->sex->idvararr=[
{"name":"aa","id":1000,"sex":0,"age":28},
{"name":"bb","id":1001,"sex":1,"age":18},
{"name":"cc","id":1002,"sex":0,"age":18},
{"name":"cc","id":1003,"sex":1,"age":18}
];
//1.升序
functionupsort(first,second,third){
returnfunction(a,b){
varv1=a[first];
varv2=b[first];
varres=v1-v2;
if(res==0){
upsort(first,second,third);
varv3=a[second];
varv4=b[second];
varres2=v3-v4;
returnres2;
if(res2==0){
upsort(first,second,third);
varv5=a[third];
varv6=b[third];
varres3=v5-v6;
returnres3;
}
}
returnres;
}
}
//2.降序
functiondownsort(first,second,third){
returnfunction(a,b){
varv1=a[first];
varv2=b[first];
varres=v2-v1;
if(res==0){
downsort(first,second,third);
varv3=a[second];
varv4=b[second];
varres2=v4-v3;
returnres2;
if(res2==0){
downsort(first,second,third);
varv5=a[third];
varv6=b[third];
varres3=v6-v5;
returnres3;
}
}
returnres;
}
}
functionsortPlugin(){}sortPlugin.prototype.str=1;//1为升序，2为降序，默认为升序sortPlugin.prototype.sortWay=function(str=this.str){
if(str==1){
console.log(arr.sort(upsort("age","sex","id")));
}elseif(str==2){
console.log(arr.sort(downsort("age","sex","id")));
}
}
varsp=newsortPlugin();sp.sortWay();
sp2.sortWay(2);
单独运行两个函数是没问题的，不知道哪里出了问题，原型链还没有吃透