Express Js || REST Api

 npm init 

or 

npm int -y

npm install --save express

what is nodemon 

npm install -g nodemon --save 

npm install --save-dev nodemon

I want to run nodemon server.js. 

const express = require('express');

const app =express();

const port = process.env.PORT ||5000;

app.get('/', (req, res)=>res.json('Hello World'));

app.listen(port,(req, res)=>{

console.log(`Server running on port ${port}`);

})

npm install --save mongoose

const express = require('express');

const mongoose =require('mongoose');

const app =express();

mongoose.connect('mongodb://localhost:27017/myapp', {useNewUrlParser:true});

const connection =mongoose.connection;

connection.once("open",()=>console.log('connection successfull'));

const port = process.env.PORT ||5000;

app.get('/', (req, res)=>res.json('Hello World'));

app.listen(port,(req, res)=>{

    console.log(`Server running on port ${port}`);

})

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Example :#1 [Post Example ]

models/userSchema.js

const mongoose = require('mongoose');

const schema = mongoose.Schema;

const User = schema({

    username:{

        type: String,

        required:true,

        unique:true,

    },

    password:{

        type:String,

        required:true

    },

    email:{

        type:String,

        required:true

    }

    })

    module.exports = mongoose.model("User", User);

....................................................................

routers/router.js

const express = require('express');

const router = express.Router();

const User = require('../model/userSchema');

router.route('/register').post((req, res)=>{

    console.log('inside user');

    const user = new User({

        username:req.body.username,

        password: req.body.password,

        email: req.body.email

    });

    user.save()

    .then(()=>{

        console.log('User Reegister Successfull');

        res.status(200).json('Okay');

    })

    .catch((error)=>{

        res.status(403).json({msg:error});

    });

   // res.json('Registered')

});

router.route("/:username").patch((req, res) => {

    User.findOneAndUpdate(

        { username: req.params.username },

        { $set: { password: req.body.password } },

        (err, result) => {

            if (err) return res.status(500).json({ msg: err });

            const msg = {

                msg: "password Successfuly updated",

                username: req.params.username,

            };

            return res.json(msg);

        })

})

router.route("/:username").delete((req, res) => {

    User.findOneAndDelete(

        { username: req.params.username },

        (err, result) => {

            if (err) return res.status(500).json({ msg: err });

            const msg = {

                msg: "User Deleted",

                username: req.params.username

            };

            return res.json(msg);

        }

    )

})

module.exports = router;

..............................................................

server.js

const express = require('express');

const mongoose =require('mongoose');

const app =express();

const userRouter = require('./routes/route');

mongoose.connect('mongodb://localhost:27017/myapp', {useNewUrlParser:true});

const connection =mongoose.connection;

connection.once("open",()=>console.log('connection successfull'));

const port = process.env.PORT ||5000;

app.get('/', (req, res)=>res.json('Hello World'));

app.use(express.json());

app.use('/user', userRouter);

app.listen(port,(req, res)=>{

    console.log(`Server running on port ${port}`);

})

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