How can I pass a variable in sort funtcion of mongobd? - mongodb

Question

I want to pass this name variable in sort function. I am getting the value of name in console.log but its not working in sort function.
var coldata = req.body.order[0].column;
var name = req.body.columns[coldata].data; // Want to pass this variable in sort()
var first = req.body.order[0].dir;
var last = req.body.order[0].dir;
var x,y;
if (first == 'asc'){
x = 1
}else{
x = -1;
}
if (last == 'asc'){
y = 1
}else{
y = -1;
}
var searchStr = req.body.search.value;
if(req.body.search.value)
{
var regex = new RegExp(req.body.search.value, "i")
searchStr = { $or: [{'firstname':regex },{'lastname': regex}] };
}
else
{
searchStr={};
}
console.log(req.body.search.value)
var recordsTotal = 0;
var recordsFiltered=0;
console.log(searchStr);
db.count({}, function(err, c) {
recordsTotal=c;
db.count(searchStr, function(err, c) {
recordsFiltered=c;
db.find(searchStr, 'firstname lastname',{'skip': Number( req.body.start), 'limit': Number(req.body.length) }, function (err, results) {
if (err) {
console.log('error while getting results'+err);
return;
}
var data = JSON.stringify({
"draw": req.body.draw,
"recordsFiltered": recordsFiltered,
"recordsTotal": recordsTotal,
"data": results
});
res.send(data);
}).sort({name:x});// Not getting value of name here
});
});
});

Answer 1

You can use an aggregation pipeline
const sort = {};
sort[name] = x
const pipeline = [
{ $match: searchStr },
{ $skip: Number( req.body.start) },
{ $limit: Number( req.body.length) },
{ $sort: sort }
];
db.aggregate(pipeline) ...