Extract Decimal from Decimal128 with Mongoose - MongoDB

Question

I\'m querying Mongo in Nodejs with Mongoose and attempting to extract the numeric value of multiple fields stored as a Decimal128. However, the value is oddly wrapped in que

Answer 1

Method 1: .

use toString(). It will convert the object to string.

find((docs) => {
   let result = docs.map((doc) => {
       if(doc.open){
          doc.open = doc.open.toString();
       }

       if(doc.close){
          doc.close = doc.close.toString();
       }

       return doc;  
   });

    //send modified output
    res.json(result);
})

output as follows:-

/*
[
  {
    "open":  "86.13",
    "close": "85.64"
  },
]
*/

Method 2: Mongodb 4.0 above,

db.myCollection.aggregate([
  {$match:{
   //...
   //...
   }},


  { $addFields : {
        open: {"$toString" : "$open"},
        close : {"$toString" : "$close"},
    }},
]);

Answer 2

This will work with any field!

It supports subdocument and arrays of subdocuments too

const MySchema = new Schema({/*... schema fields ...*/});


const decimal2JSON = (v, i, prev) => {
  if (v !== null && typeof v === 'object') {
    if (v.constructor.name === 'Decimal128')
      prev[i] = v.toString();
    else
      Object.entries(v).forEach(([key, value]) => decimal2JSON(value, key, prev ? prev[i] : v));
  }
};

MySchema.set('toJSON', {
  transform: (doc, ret) => {
    decimal2JSON(ret);
    return ret;
  }
});

mongoose.model('MyModel', MySchema);

Usage:

MyModel.findOne().then(data => console.log(data.toJSON());

Answer 3

Working solution

const mongoose = require('mongoose')
const parentSchemaSymbol = mongoose.model('Stock')

exports.dbFetch = (req, res) => {
  let curValueDbFetch = req.params.symbol

  const query = { symbol: `${curValueDbFetch}` }
  const projection = { _id: 0, data: 1 }

  parentSchemaSymbol.findOne(query, projection).sort({ date: -1 }).then(doc => {
    let chartData = doc.data.map(item => {
      return {
        date: parseFloat(item.date), // the date
        open: parseFloat(item.open), // open
        high: parseFloat(item.high), // high
        low: parseFloat(item.low), // low
        close: parseFloat(item.close), // close
        volume: parseFloat(item.volume)// volume
      }
    })
    res.send(chartData)
  })
    .catch(e => {
      console.log(e)
    })
}