How to create object from array elements to be passed into mongodb aggregation in mongoose and node.js?

Question

I've a usecase in which I'll get dynamic field names in an array. I need to pass those fields to the mongo db aggregation query to get the sum of that field values in a given month. I need to remove the timeStamp & deviceId fields in array.

let jsonObj = [ { name: "heat", value: "HEAT" }, { name: "humidity", value: "HUMIDITY" }, { name: "deviceId", value: "DEVICEID" }, { name: "timeStamp", value: "TIMESTAMP" } ]; let vList = []; jsonObj.forEach(async data => { if (!data.name.match(/time/g) || !data.name.match(/deviceId/g)) { vList.push(data.name); //Should exclude timestamp & deviceId (case-insensitive) } }); let variableObj = []; vList.forEach(async data => { let k = "{" + '"$sum":"$' + data + '"}'; // console.log(k) k = JSON.parse(k); variableObj.push(data + ":" + k); });

Then resultant array looks like the following.

[ 'heat:{"$sum":"$heat"}', 'humidity:{"$sum":"$humidity"}', 'timeStamp:{"$sum":"$timeStamp"}', 'deviceId:{"$sum":"$deviceId"}' ]

Am not getting how to remove the single quotes around each item and how to pass them to query.

My query is:

db.collection(templateId).aggregate([ { $match: { entryDayTime: { $lt: new Date(lastDay), $gte: new Date(firstDay) } } }, { $group: { _id: "$deviceId", Count: { $sum: 1 } // Should pass those array elements here like, //heat:{"$sum":"$heat"}, //humidity:{"$sum":"$humidity"} } }, { $sort: { entryDayTime: -1 } } ]);

Ashish Modi · Accepted Answer · 2019-12-30 10:03:11Z

This should work.

const jsonObj = [ { name: "heat", value: "HEAT" }, { name: "humidity", value: "HUMIDITY" }, { name: "deviceId", value: "DEVICEID" }, { name: "timeStamp", value: "TIMESTAMP" } ]; const filteredJson = jsonObj.filter(i => i.name !== "deviceId" && i.name !== "timeStamp"); const groupQuery = { $group:{ _id:"$deviceId", Count:{$sum:1} } }; filteredJson.forEach(row => { groupQuery.$group[row.name] = {"$sum": `$${row.name}`}; }); console.log(groupQuery);

Hope this helps. All you need to do is now, insert the $group with the variable prepared above.

ambianBeing · Accepted Answer · 2019-12-30 10:13:49Z

You could create the whole group object together and pass it onto the $group stage. Also remove those async keywords, the iterations are not asynchronous.

Note: The if clause should have && to exclude both keywords and i flag is for case-insensitivity in regex. And creation of the target object can be completed in the first iteration itself.

let jsonObj = [ { name: "heat", value: "HEAT" }, { name: "humidity", value: "HUMIDITY" }, { name: "deviceId", value: "DEVICEID" }, { name: "timeStamp", value: "TIMESTAMP" } ]; let groupObject = { _id: "$deviceId", Count: { $sum: 1 } }; jsonObj.forEach(data => { if (!data.name.match(/timestamp/gi) && !data.name.match(/deviceid/gi)) { groupObject[data.name] = { $sum: "$" + data.name }; } }); console.log(groupObject);

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