Can not fetching the exact value with mongoose - node.js

Question

I want to fetch data from mongodb using mongoose and send it as a response, but I don't get the exact answer, what's my mistake?
My codes are as below:
Firstly My model file:
* I'm inserting data in bulk with create()
const express = require('express');
const mongoose= require('mongoose');
const Schema = mongoose.Schema;
const ourDataSchema = new Schema ({
rank : Number,
totalPoints : Number
});
const rankTotalpoint = mongoose.model("rankTotalpoint", ourDataSchema);
const ourData = [
{rank : 1, totalPoints : 2000},
{rank : 2, totalPoints : 1980},
{rank: 3, totalPoints : 1940},
{rank: 4, totalPoints : 1890},
{rank : 5, totalPoints : 1830},
{rank : 6, totalPoints : 1765},
{rank : 7, totalPoints : 1600},
{rank : 8, totalPoints : 1565},
{rank : 9, totalPoints : 1465},
{rank : 10, totalPoints : 1450}
];
rankTotalpoint.create(ourData, function (error, data) {
if (error) {
console.log(error)
}
else {
console.log('saved!');
}
});
exports.result = function (param) {
const finalresult = rankTotalpoint.aggregate([
{
$project: {
diff: {
$abs: {
$subtract: [
param, // <<<----------------------- THIS IS THE USER SUPPLIED VALUE
"$totalPoints"
]
}
},
doc: "$$ROOT"
}
},
{
$sort: {
diff: 1
}
},
{
$limit: 1
},
{
$project: {
_id: 0,
rank: "$doc.rank"
}
}
])
return finalresult;
};
And my controller file codes where I imported my above(result) function to it :
const express = require('express');
const model = require('../model/logic');
exports.index = (req, res, next) => {
res.status(200).json({message : 'INSERT INPUTS HERE'});
};
exports.getUserData = (req, res, next) => {
const literature = req.body.literature * 4;
const arabic = req.body.arabic * 2;
const religion = req.body.religion * 3;
const english = req.body.english * 2;
const math = req.body.math * 4;
const physics = req.body.physics * 3;
const chemistry = req.body.chemistry *2;
//user supplied value
const TOTALPOINT = literature + arabic + religion + english + math + physics + chemistry;
let result = model.result(TOTALPOINT);
res.status(200).json(result);
};
And finally that's the response I get with postman :
{
"_pipeline": [
{
"$project": {
"diff": {
"$abs": {
"$subtract": [
0,
"$totalPoints"
]
}
},
"doc": "$$ROOT"
}
},
{
"$sort": {
"diff": 1
}
},
{
"$limit": 1
},
{
"$project": {
"_id": 0,
"rank": "$doc.rank"
}
}
],
"options": {}
}
What I want to get?
I want to get a rank based on the user input(TOTALPOINT) that I'm getting, So instead of sending the above response, I just want to send back the rank to the user.
If the user value matches a totalpoints, send it's rank as a response and if the exact value doesn't exist, find the closest totalPoints and send the rank as response.
Like this:
[
{
"rank": 5
}
]
Thank you

Answer 1

Your issue is because Mongoose is promise/async based. You are not awaiting anything, so your code returns a variable that has not been set yet by your query..
I was testing using 2 files: myMongoose.js and index.js..
// myMongoose.js
// ** CODE THAT SAVES DATA TO DATABASE HAS BEEN REMOVED FOR BREVITY **
require('dotenv').config();
const mongoose = require('mongoose');
const RankTotalpointSchema = new mongoose.Schema({
rank: Number,
totalPoints: Number
});
mongoose.set('useCreateIndex', true);
const mongoConnection = mongoose.createConnection(process.env.MONGO_DB_STRING, {
useUnifiedTopology: true,
useNewUrlParser: true,
useFindAndModify: false,
});
const RankTotalpoint = mongoConnection.model("RankTotalpoint", RankTotalpointSchema, 'Testing');
/**
* ~~~~~~ **** THIS HAS TO BE AN ASYNC FUNCTION **** ~~~~~~
*/
exports.result = async function (param) {
const finalresult = await RankTotalpoint.aggregate([{
$project: {
diff: {
$abs: {
$subtract: [
param, // <<<----------------------- THIS IS THE USER SUPPLIED VALUE
"$totalPoints"
]
}
},
doc: "$$ROOT"
}
},
{
$sort: {
diff: 1
}
},
{
$limit: 1
},
{
$project: {
_id: 0,
rank: "$doc.rank"
}
}
])
return finalresult;
};
...and then in index.js:
// index.js
const { result } = require('./myMongoose');
// Use it like this:
async function init() {
try {
const d = await result(1800);
console.log(d);
} catch (err) {
console.error(err);
}
}
init(); // -> [ { rank: 5 } ]
// --------------------------------------------------------------------
// ...or like this:
(async () => {
try {
const d = await result(1800);
console.log(d); // -> [ { rank: 5 } ]
} catch (err) {
console.error(err);
}
})()
// --------------------------------------------------------------------
// ...or like this:
result(1800)
.then(d => console.log(d)) // -> [ { rank: 5 } ]
.catch(err => console.error(err))