MongoDB Shell - Print the first element of an array

Question

I'm trying to use the function print in "NoSQL Manager for MongoDB 4.9.10.2" to print the first element of an array. I'm trying to do the following:

    var start = ISODate("2018-12-18T03:00:00.000Z"); 
var end = ISODate("2018-12-19T02:59:59.000Z"); 

db.moicaTickets.aggregate([

    { $match : 
        { asunto:{$exists:true},
          asunto: {$ne:null},
          tiempos:{$exists:true}, 
          tiempos: {$ne:null},
          problemas:{$exists:true},
          creado:{$exists:true}, 
          "creado.lastEvent_tc": { $gt: start, $lt: end } }},
    { $project: 
        { pFecha: { $dateToString: { format: "%Y-%m-%d", date: "$creado.lastEvent_tc", timezone: "-03:00" } }, 
        asunto: 1, 
        tiempos: 1, 
        nroTkt: 1,
        losProblemas: { $arrayElemAt: ["$problemas",0]},
        primerProblema: "$losProblemas.nombre",
        primera: { $arrayElemAt: ["$tiempos",0]}}},
    { $addFields: { "lacola":{ "$toObjectId": "$primera.cola" }}},
    { $lookup:
       {
         from: "moicaTicketsColas",
         localField: "lacola",
         foreignField: "_id",
         as: "nombreCola"
         }}

         ]).forEach(function(doc){
         print(doc.nroTkt+";"+doc.nombreCola.0.arbol+";"+doc.pFecha+";"+doc.asunto.titulo+";"+doc.primerProblema);
})

But i get the next error:

2018-12-19T12:00:06.660-0300 E QUERY    [js] SyntaxError: missing ) after argument list @(shell):29:44

This is an example of "nombreCola": "nombreCola" : [ { "_id" : ObjectId("5b55f8a351b9979f1e417b43"), "nombre" : "Al. Fuentes", "padre" : "5ad8a36251b99792eb60418a", "nivel" : 2, "creado" : { "creador" : "gerodriguez", "lastEvent_st" : "23-07-2018 12:47:47", "lastEvent_ts" : 1532360867, "lastEvent_tc" : ISODate("2018-07-23T15:47:47.377Z") }, "arbol" : "Ceop - Noc - Al. Fuentes" } ] — NGabioud
– NGabioud, Commented Dec 19, 2018 at 17:08

NGabioud · Accepted Answer · 2018-12-19 17:28:36Z

1

I solved it, what goes outside the query is JavaScript, so the proper way to print an array (or in this case, get the first element) is:

print(doc.nroTkt+";"+doc.nombreCola[0].arbol+";"+doc.pFecha+";"+doc.asunto.titulo+";"+doc.primerProblema);

Thank you!

answered Dec 19, 2018 at 17:28

NGabioud

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