Crud operations in Express

These are the middleware needed for CRUD operations in express

//web framework for node.js
var express= require('express')
//Gives an instance of express
var app=express();
//Used for post request and forms
var bodyParser=require('body-parser');
//MongoDB Object modeling tool designed to work in asynchronous environment
var mongoose = require('mongoose');

Enable CORS

//Enable cors 
app.use(function(req, res, next) {
  res.header("Access-Control-Allow-Origin", "*");
  res.header("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, 

   Accept");
  next();
});

Connect to the database

//connect to mongoose
mongoose.connect('mongodb://127.0.0.1:27017/Ecommerce');

Create models

//Model for fetching users
var userSchema=mongoose.Schema({
    firstName:{
      type:String,
      required:true
    },
    lastName:{
      type:String
      
    }
});
//User Model
var User=mongoose.model("users",userSchema)

GET

Find all users using Get

//Using find to fetch all the users in the db
app.get("/api/Users",function(req,res){
  User.find({},function (err,user){
    if(err)
    {
       console.log(err);
       res.send(err);
    }
    else
   {
     console.log(user);
    res.send(user);}
  });

});

Filter users using querystring

app.get("/api/Users",function(req,res){

//Get the filter query
  var query=req.query;
      User.find(query, function(err, user) {
      
           if (err)
                res.send(err);
            else
                res.send(user)
            //res.json(user);
        });
  });

Fetch users using ID

app.use('/api/Users/:_id',function(req,res,next){
  console.log('custom middleware');
      //Find based on ID
       User.findById(req.params._id, function(err, user) {
             if (err)
                res.status(500).send(err);
              //fetch user and send it to next function
             else if(user)
             {
                    req.user=user;
               next();
                res.status(200).send('Success');
             }
            else
            {
              res.status(404).send('no user found');
            }
        });
});

Use bodyparser to allow express to read the body and parse it into JSON object

//Use bodyParser
app.use(bodyParser.urlencoded({extended:true}));
app.use(bodyParser.json());

POST

Post to save new users

//Post
app.post('/api/Users',function(req, res) {
  var users = new User(req.body);
  
  //save users
   users.save(function(err) {
    //Check for error
    if (err) {
      return res.send(err);
    }
    else{
    console.log('Success');
    res.send(users)
    }
  });
  //res.send('Responding');*/
 });

validate post method using PostMan

Validate using fiddler

PUT

Find the specified document and update the record

/**
  * PUT
*/
  app.put('/api/Users/:_id',function(req,res){
  //Get the filter query
      User.findById(req.params._id, function(err, user) {
        if(err)
          {
            res.send(err);
          }
        //Update 
        else
        {
          
          user.firstName=req.body.firstName;
          user.lastName=req.body.lastName;
          user.save(function(err)
          {
               if (err) {
                        return res.send(err);
                      }
              else{
              console.log('Edit Succeded');
              res.send(users)
            }
          });
          res.json(user)
        }
    });
  });

Validate put operation using postman

Updated document in the collection.

PATCH

The HTTP methods PATCH can be used to update partial resources

In this example we need to delete the is from the parser as we cannot update the id.

/**
  * PATCH
 */
 app.patch('/api/Users/:_id',function(req,res){
     //We do not want ot update the ID. We need to delete ID from the body parser
     if(req.body._id)
     {
        delete req.body_id;
     }
     //Fetch all the keys in the body parser
      for(var u in req.body){
      //assignind the body content to the req object
        req.user[u]=req.body[u];
      }
        req.user.save(function(err){
           if (err)
                res.status(500).send(err);
              //fetch user and send it to next function
             else {
                 res.json(req.user);
             }
        });
       
    });

Validate patch in postman

Update document in the collection

DELETE

For delete we need to use the remove function.

/**
  * DELETE
 */  
app.delete('/api/Users/:_id',function(req,res){
  //delete the document frmom the mongodb collection
  req.user.remove();
 
});

Validated delete in postman

Updated user collection in DB