node.js导出json,csv格式

var nation_export_save = function(req, res) {
var encode = req.body.encode;（encode为‘utf8’ or 'GBK'）
var sname = req.body.sname;
var items = req.body.items;
Nation.find({}, function(err, nations) {
if (sname == 'JSON') {
res.attachment('nation.txt');
res.send(nations);
} else if (sname == 'CSV') {
var ites = [];
var lines = items.split(',');
for (var i = 0; i < lines.length; i++) {
ites.push(lines[i]);
};
json2csv({
data: nations,
fields: ites
}, function(err, csv) {
var iconv = new Iconv('UTF-8', encode);
content = iconv.convert(csv);
res.attachment('nation.csv');
res.send(content);
})

};
})
}