Empty response object in MongoDb - node.js

Question

I am trying to get all documents in mongo collection but instead i am getting empty response. my database name is taskDb which has a collection named item in which all the documents are stored. I think maybe there is some problem with schema but mongo is schema less db so i am not able to find the solution.
index.js
var express = require('express');
var app = express();
var bodyParser = require('body-parser');
var mongoose = require('mongoose');
var cors = require('cors');
app.use(bodyParser.json());
app.use(cors());
Items = require('./items.js');
mongoose.connect('mongodb://localhost/taskDb');
var db = mongoose.connection;
app.get("/",(req, res)=> {
res.send('Visit /api/*****');
});
app.get("/api/items",(req, res)=> {
Items.getItems(function(err, items){
if(err){
throw err;
}
console.log(res.json(items));
res.json(items);
});
});
// app.get("/api/matches",(req, res)=> {
// Matches.getMatches(function(err, matches){
// if(err){
// throw err;
// }
// res.json(matches);
// });
// });
// app.get("/api/deliveries/:playerName",(req, res)=> {
// Deliveries.getPlayerStats(req.params.playerName ,function(err, deliveries){
// if(err){
// throw err;
// }
// res.json(deliveries);
// });
// });
app.listen(3005,()=>{
console.log('Listening on port 3005...');
});
item.js
var mongoose = require('mongoose');
var itemSchema = mongoose.Schema({
_ID:{
type: String,
required: true
},
ITEM:{
type: String,
required: true
},
KEY:{
type: Number,
required: true
},
STATUS:{
type: String,
required: true
}
});
var Item = module.exports = mongoose.model('item', itemSchema);
// module.exports.getPlayerStats = function (playerName, callback) {
// Deliveries.aggregate([{$project:{_id: 1,batsman: 1 ,batsman_runs: 1, dismissal:{
// $cond: [ { $eq: ["$player_dismissed", playerName ] }, 1, 0]
// }}},{ $match: { batsman: playerName } },
// { $group: {_id: "$batsman", total_runs: { $sum: "$batsman_runs" },total_dismissal: { $sum: "$dismissal"}}}
// ], callback);
// }
module.exports.getItems = function (callback, limit) {
Item.find(callback).limit(limit);
};

Answer 1

There are two issues I see in getItems function:
Condition for find() is not specified. In case you want to read all records, you can specify it as empty object.
Limit parameter is not being passed from your request handler to getItems function. You would either need to default it to some number or handle the scenario where limit won't be passed.
Modifying getItems() to something like below should work:
module.exports.getItems = function (callback, limit) {
Item.find({}, callback).limit(limit || 20); // Default limit to a feasible number
};
Also, you can pass limit to getItems() function from request handler if you want to override default:
app.get("/api/items",(req, res)=> {
Items.getItems(function(err, items){
if(err){
throw err;
}
console.log(res.json(items));
return res.json(items);
}, 50); // Pass limit
});