面试题：CouchDB中Map函数如何对复杂嵌套数据结构进行转换应用

Question

假设在CouchDB中有一个文档，其数据结构为 {"name":"John","hobbies":[{"name":"reading","details":{"favoriteGenre":"fiction"}},{"name":"traveling","details":{"visitedCountries":["USA","UK"]}}]} 。请编写一个Map函数，将其转换为包含人员姓名及每个爱好的简单信息的新格式，例如 {"name":"John","hobby_name":"reading","hobby_detail":"fiction"} 和 {"name":"John","hobby_name":"traveling","hobby_detail":"USA,UK"} 这样的形式。

Answer 1

function(doc) {
    if (doc.name && doc.hobbies) {
        doc.hobbies.forEach(function(hobby) {
            var hobby_detail;
            if (hobby.name === "reading") {
                hobby_detail = hobby.details.favoriteGenre;
            } else if (hobby.name === "traveling") {
                hobby_detail = hobby.details.visitedCountries.join(",");
            }
            emit(null, {
                name: doc.name,
                hobby_name: hobby.name,
                hobby_detail: hobby_detail
            });
        });
    }
}