NodeJS MongoDB Pass parameter in the aggregation pipeline - node.js

Question

How to pass an parameter to the aggregation?
I'm getting the params and trying to pass it using $match operator but query returns empty array:
app.get('/api/:name', function(req, res){
var name = req.params.name;
console.log(name);
db.collection('coll').aggregate([{$match: {name: '$name'}}, {$unwind: { path: "$dates", includeArrayIndex: "idx" } }, { $project: { _id: 0, dates: 1, numbers: { $arrayElemAt: ["$numbers", "$idx"] }, goals: { $arrayElemAt: ["$goals", "$idx"] }, durations: { $arrayElemAt: ["$durations", "$idx"]}}}]).toArray(function(err, docs) {
if (err) {
assert.equal(null);
}
else {
console.log(docs);
res.json(docs);
}
});
})
Should I care about order of the operators in pipeline?

Answer 1

Try the following code:-
app.get('/api/:name', function(req, res){
var name = req.params.name;
var query = [{$match: {'name': name}}, {$unwind: { path: "$dates", includeArrayIndex: "idx" } }, { $project: { _id: 0, dates: 1, numbers: { $arrayElemAt: ["$numbers", "$idx"] }, goals: { $arrayElemAt: ["$goals", "$idx"] }, durations: { $arrayElemAt: ["$durations", "$idx"]}}}];
db.collection('coll').aggregate(query).toArray(function(err, docs) {
if (err) {
assert.equal(null);
}
else {
console.log(docs);
res.json(docs);
}
});
})

Answer 2

It seems you never use variable called name.
Try this, change {$match: {name: '$name'} to {$match: {name: name}.

Answer 3

try,
{$match: {'name': req.params.name}}
this works for me

Answer 4

Mongoose does not cast pipeline stages. The below will not work unless _id is a string in the database
new Aggregate([{ $match: { _id: '00000000000000000000000a' } }]);
// Do this instead to cast to an ObjectId
new Aggregate([{ $match: { _id:
mongoose.Types.ObjectId('00000000000000000000000a') } }]);
API URL: https://mongoosejs.com/docs/api.html#aggregate_Aggregate