nodejs mongodb ，从数据库中没有得到任何结果

Question

Issue with working on data from MongoDb

Connecting to MongoDb successfully ,

but on find command , it should return an empty collection , yet nothing is returned.

what could be the issue , or how it could be monitored by some error messaging.

Thanks.

Project dependencies

"dependencies": {
"body-parser": "^1.19.0",
"epxress": "0.0.1-security",
"express": "^4.17.1",
"nodemon": "^2.0.2"

}

mongoose.js

const mongoose = require('mongoose');

mongoose.Promise = global.Promise;
mongoose.connect('mongodb://localhost:27017/ListsDB', { useNewUrlParser: true, useUnifiedTopology: true}).then( ()=> {
    console.log("Connected to MongoDbB successfully ");
}).catch( (e) => {
    console.log("Error while attempting to connect to MongoDB");
    console.log(e);
});

mongoose.set('useCreateIndex', true);
mongoose.set('useFindAndModify', false);

module.exports = {
    mongoose
};

list.model.js

const mongoose = require('mongoose');

const ListSchema = new mongoose.Schema({
   title: {
       type: String,
       required: true,
       minlength: 1,
       trim: true
   }
})

const List = mongoose.model('List', ListSchema);

module.exports = { List }

app.js Not Working

const express = require('express');
const app = express();

const bodyParser = require('body-parser');

const { List, Task } = require('./db/models');

app.use(bodyParser.json());

app.use(function(req, res, next) {
    res.header("Access-Control-Allow-Origin", "*"); // update to match the domain you will make the request from
    res.header("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Accept");
    next()
  })

app.get('/lists', (req,res) => {
    // We want to return an array of all the lists in the database
    List.find({}).then( (err, lists)=> {
        res.send(lists)
    })
})

app.listen(3000, () => {
    console.log("Server is listening on port 3000");
})

Answer 1

Try using this syntax

   app.get('/lists', (req,res) => {
     List.find({}).then( lists => {
        res.send(lists)
     }).catch(err =>
        console.log(err)
     );
   })

Answer 2

You are passing multiple argument in then block. Then is only accept single argument that is mark as success data. If you want to show errors also you have to pass in error argument in catch block.

Try This code :

    const express = require('express');
    const bodyParser = require('body-parser');
    const List = require('./listModel');
    const mongoConnection = require('./mongoose');
    const app = express();

app.use(bodyParser.json({
    limit: '20mb',
    extended: true
}));
app.use(bodyParser.urlencoded({
    extended: true
}));

app.get('/lists', (req,res) => {
     List.find().then( lists => {
                res.send(lists)
          }).catch(err =>
                res.send(err)
          );
 });

app.listen(3100, () => {
    console.log("Server is listening on port 3100");
})