在XML中创建对象的目的是什么？

Question

var duplicates = ["a","a","b","c","a"];
var withoutDuplicates = duplicates.filter(function(currentValue, index) {
    return duplicates.indexOf(currentValue) == index;
});
console.log(withoutDuplicates); // Array [ "a", "b", "c" ]

此代码在XML中的用途是什么？