Web Technology Experts Notes

Thursday, 29 June 2017

How to upload file/images using nodejs?

I am assuming you already have install NodeJS in your System, Just follow below simple steps

Install below module ?

npm install express

npm install fs

npm install body-parser

npm install multer

HTML Part?
Create a file upload.html and add below code in file.


        <form action="http://127.0.0.1:8081/file_upload" enctype="multipart/form-data" id="uploadForm" method="POST" onsubmit="return uploadForm()">
Upload File: <input name="file" size="50" type="file" />
            <br />
<input type="submit" value="Upload File" />
        </form>

Node JS Code create upload.js file and add below code.

var express = require('express');
var app = express();
var fs = require("fs");

var bodyParser = require('body-parser');
var multer  = require('multer');

app.use(express.static('public'));
app.use(bodyParser.urlencoded({ extended: false }));
var upload = multer({ dest: './tmp' });

app.get('/upload.html', function (req, res) {
   res.sendFile( __dirname + "/" + "upload.html" );
})

app.post('/file_upload', upload.single('file'), function (req, res) {
    console.log(req.file);
    
    
   var file = __dirname + "/public/upload/" + req.file.originalname;
   
   
   fs.readFile( req.file.path, function (err, data) {
      fs.writeFile(file, data, function (err) {
         if( err ){
            console.log( err );
            }else{
               response = {
                  message:'File uploaded successfully',
                  filename:req.file.originalname
               };
            }
         console.log( response );
         res.end( JSON.stringify( response ) );
      });
   });
})

var server = app.listen(8081, function () {
   var host = server.address().address
   var port = server.address().port
   
   console.log("Example app listening at http://%s:%s", host, port)
})

Question: Following are sample of file object in ?

 { fieldname: 'file',
  originalname: 'Desert.jpg',
  encoding: '7bit',
  mimetype: 'image/jpeg',
  destination: './tmp',
  filename: '3570feafa527690b90b972a1bf085bdd',
  path: 'tmp\\3570feafa527690b90b972a1bf085bdd',
  size: 845941 }

Create following empty folder?

/tmp

/public

/public\upload

Now Start the Node project?

node upload.js

Access the Web URL?

http://127.0.0.1:8081/upload.html

Select the File and click on Upload File?
It will show below simiar message

{"message":"File uploaded successfully","filename":"Desert.jpg"}

Question: What port we have used here?
We have used 8081 port, but you can change it by change in upload.js

Wednesday, 28 June 2017

What is a promise and how to use with mongoose?

Question: What is a promise?
A promise is an abstraction for asynchronous programming.
It's an object that proxies for the return value thrown by a function that has to do some asynchronous processing.

Question: How does promise work?
The Promise constructor takes a function (an executor) that will be executed immediately and passes in two functions: resolve , which must be called when the Promise is resolved (passing a result), and reject , when it is rejected (passing an error)

Question: Give example of promise work in mongoose?

User.update({id: 100}, {$inc: { views: 1 }}).limit(1).exec();

Here execute multiple function in one line is promise.

Question: How to setup mongoose with promise?

var mongoose = require('mongoose');
mongoose.Promise = require('bluebird');
mongoose.connect('mongodb://localhost:27017/dbname');
var db = mongoose.connection;
db.on('error', console.error.bind(console, 'connection error:'));
db.once('open', function() {
    console.log("MongoDB connected Successfully.!");
});

Question: How to Add the data in mongoDb with mongoose?

//Ajax chat messages
var AjaxChatMessageSchema = mongoose.Schema({
    id: Number,
    userID: Number,
    userName: String,
    userRole: String,
    channel: String,
    dateTime: String,
    ip: String,
    text: String,
    status: String,
    vid: Number
}, {collection: 'ajax_chat_messages'});
var AjaxChatMessage = mongoose.model('ajax_chat_messages', AjaxChatMessageSchema);

var saveData={id:11, userName:'testuser',text:'hello user'}
var AjaxChatMessageDtls = new AjaxChatMessage(saveData);
AjaxChatMessageDtls.save(function(err) {
    if (err) {
        console.log("Error while saving the details");
        response.success = 0;
        res.send(response);
    } else {
        response.success = 1;        
        res.send(response);
    }
});

Question: How to do decrement the value by 1?

AjaxChatMessage.update({id: 100}, {$inc: { views: -1 }}).limit(1).exec();

Question: From where we can read more about promise?
http://mongoosejs.com/docs/promises.html

Thursday, 22 June 2017

Express JS - use res.sendFile - use EJS template - Set and Get Session data

setup of EJS template in Express? Get/Set session in Express? How to setup static path in Express

Question: What is res.sendFile() in NodeJS?
It is a simple way to deliver an HTML file to the client.

Example of sendFile

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

app.get('/', function(req, res) {
    res.sendFile(path.join(__dirname + '/index.html'));
});
app.listen(8080);

Question: How to use EJS in Express?
Install the EJS

npm install ejs --save

Set the Engine as EJS in node server

app.set('view engine', 'ejs');

render file from node server

app.get('/', function(req, res) {  
  res.render('index', { title: 'The index page!' })
});

Use the parameter in File

<%= title %>

Question: How to Get/Set session in Express?
install session

npm instal express-session --save

Initiaization the session

var session = require('express-session');
app.use(session({
    secret: 'SECRETKEY',
    name: 'SESSION NAME',
    proxy: true,
    resave: true,
    saveUninitialized: true
}));

Set the Session

var sessionData
app.get('/set-the-session', function(req, res) {    
    sessionData = req.session;
    var userDetails = {}    

    //set the session
    sessionData.isLogin = 1;
    sessionData.name = req.body.name;
    sessionData.email = req.body.email;
});

Get the Session

app.get('/get-session', function(req, res) {    
    sessionData = req.session;
    userDetails.isLogin = sessionData.isLogin;
    userDetails.name = sessionData.name;
    userDetails.email = sessionData.email;
    res.send(userDetails);    
});

Question: How to setup static path in Express?

var express = require('express');
var app = express();
app.use(express.static('public'))

create file in : images/kitten.jpg, Now you can access

http://localhost:3000/images/kitten.jpg

Question: Session is not working with ajax call
Explanation
URL: http://127.0.0.1:8080/getphotoaccess?uid=7177
When running in browser, session is working fine.
When running with ajax call, session is not working

Solution
You need to add xhrFields: {: true},in ajax request.
For Example:

$.ajax({
    type: "GET",
    url: "getphotoaccess?uid=7177",            
    dataType: "json",    
    xhrFields: {
            withCredentials: true
       },            
    success: function(resData){

    }
});

Tuesday, 20 June 2017

Socket.IO module with nodeJs tutorial

How to send message from Node(server) to browser(client) and vice versa? How to connect/disconnect to the room.

Question: What is socket.io module?
Socket.IO is a JavaScript library for realtime web applications.
It enables realtime, bi-directional communication between web clients and servers.
It has two parts
a) client-side library that runs in the browser.
b) server side that run in browser.

Question: Give example of real time application?

Instant messengers like facebook notification/message.
Push Notifications like when someone tags you in a picture on facebook, you receive an instant notification.
Collaboration applications like multiple user editing same file.
Online gaming

Question: Why we use socket.io?

bi-directional communication channel between a client and a server.
When an event occur, socket get notify and let to know the single client OR all clients.
It is trust application and used by Microsoft Office, Yammer, Zendesk, Trello, and numerous other organizations.

Question: How to install socket.io in Web and Server?
In Browser (client)

<script src="https://cdnjs.cloudflare.com/ajax/libs/socket.io/2.0.3/socket.io.js"></script>

In NodeJS

npm install socket.io

var io = require('socket.io')

Question: How get to know, if user is connect/disconnect?
In Server(Node)

var app = require('express')();
var http = require('http').Server(app);
var io = require('socket.io')(http);

app.get('/', function(req, res){
  res.sendfile('index.html');
});

//Whenever someone connects (execute when come in Web page)
io.on('connection', function(socket){
  console.log('A user connected');

  //Whenever someone disconnects (execute when Leave the web page)
  socket.on('disconnect', function () {
    console.log('A user disconnected');
  });

});

http.listen(3000, function(){
  console.log('listening on *:3000');
});

In Browser

 var socket = io.connect('http://127.0.0.1:3000');

Question: How to get to know, when new user comes in browse?

OR
Question: How to send message from Client(Browser) to Server(Node)?
In Server

 
socket.on('adduser', function(name, email, uid) {
    //name, email, and uid of user
    console.log('New user comes in web page');
});

In Browser>

 
socket.emit('adduser', 'Robin Sharma','robinsharma@no-spam.ws',2555);

Question: How to send message from Server(Node) to Client(Browser)?
In Server

socket.emit('newRequestCome', 'name','myself send request'); //Send message to socket (Same window)
socket.broadcast.to(roomName).emit( 'newRequestCome','name','message'); //Send message to all socket (Other windows in same Room)

In Browser

 
socket.on('newRequestCome', function(name, message) {                        

});

Question: How to join the room and send message?
Join the room

io.on('connection', function(socket){
  socket.join('someNo12');
});

Question: How to send message the room?
Send message to the room

io.in('someNo12').emit('some event');
//io.to('someNo12').emit('some event');

Monday, 19 June 2017

underscore module with nodeJs tutorial

Underscore is a JavaScript library that provides a lot of useful helper functions to fast the node development. following are list of available array/object functions.

Question: What is underscore module?
Underscore is a JavaScript library that provides a lot of useful functional helpers without extending any built-in objects.

Question: How to install async module?

npm install underscore

Question: How to include request module in node project?

var _ = require("underscore");

Question: Give an example of each in underscore?

 
_.each(['Understand', 'underscore', 'Module'], function(value,pos){
    console.log(value+' stored at '+pos);    
});

Output

Understand stored at 0
underscore stored at 1
Module stored at 2

Question: What are other collections in underscore module?

each
map
reduce
reduceRight
find
filter
where
findWhere
reject
every
some
contains
invoke
pluck
max
min
sortBy
groupBy
indexBy
countBy
shuffle
sample
toArray
size
partition

Question: How to create a range array?

 
var lists=_.range(5);
console.log(_.first());

Question: How to get first nth element from array?

 
var lists=["One","two","three","four", "five"];
console.log(_.first(lists)); //One
console.log(_.first(lists,2)); //One two
console.log(_.first(lists,3)); //One two three

Question: How to check a variable is empty OR Not ?

var name=''
console.log(_.isEmpty(name));//true

name='Hello User'
console.log(_.isEmpty(name));//false

Question: What are array functions in underscore module?

first
initial
last
rest
compact
flatten
without
union
intersection
difference
uniq
zip
unzip
object
indexOf
lastIndexOf
sortedIndex
findIndex
findLastIndex
range

Question: How to get key value of an object data?

 
var lists={1:"One",2:"two",3:"three",4:"four", 5:"five"};
console.log(_.keys(lists)); //1,2,3,4,5

Question: What are the object functions in underscore module?

 
keys
allKeys
values
mapObject
pairs
invert
create
functions
findKey
extend
extendOwn
pick
omit
defaults
clone
tap
has
matcher
property
propertyOf
isEqual
isMatch
isEmpty
isElement
isArray
isObject
isArguments
isFunction
isString
isNumber
isFinite
isBoolean
isDate
isRegExp
isError
isNaN
isNull
isUndefined

Friday, 16 June 2017

Async module with NodeJs tutorial

Example of parallel, concat and logs example in async? List all the methods available in async

Question: What is async module?
Async is a utility module which provides straight-forward, powerful functions for working with asynchronous JavaScript.

Question: How to install async module?

npm install async

Question: How to include request module in node project?

var async = require('async');

Question: Concatenate the files from different directories?

 
async.concat(['data', 'data1'], fs.readdir, function(err, files) {
    if (err) {
        return console.log(err);
    }    
    /*files is now a list of filenames that exist in the 3 directories*/
    console.log(files);    
});

Question: What are other collection methods available in async ?

concat
concatSeries
detect
detectLimit
detectSeries
each
eachLimit
eachOf
eachOfLimit
eachOfSeries
eachSeries
every
everyLimit
everySeries
filter
filterLimit
filterSeries
groupBy
groupByLimit
groupBySeries
map
mapLimit
mapSeries
mapValues
mapValuesLimit
mapValuesSeries
reduce
reduceRight
reject
rejectLimit
rejectSeries
some
someLimit
someSeries
sortBy
transform

Question: Give an example of parallel in async?

async.parallel([
    function(callback) {
        setTimeout(function() {
            callback(null, 'one');
        }, 200);
    },
    function(callback) {
        setTimeout(function() {
            callback(null, 'two');
        }, 100);
    }
],
// optional callback
function(err, results) {
        console.log(results); //['one','two']
});

Question: What other control methods in async?

applyEach
applyEachSeries
auto
autoInject
cargo
compose
doDuring
doUntil
doWhilst
during
forever
parallel
parallelLimit
priorityQueue
queue
race
retry
retryable
seq
series
times
timesLimit
timesSeries
tryEach
until
waterfall
whilst

Question: Give an example of async.log?

var hello = function(name, callback) {
    setTimeout(function() {
        callback(null, 'hello ' + name);
    }, 1000);
};
async.log(hello, 'World 1'); //Hello World 1
async.log(hello, 'World 2'); //Hello World 2
async.log(hello, 'World 3'); //Hello World 3

Question: What other Utiles methods in async?

Utils
apply
asyncify
constant
dir
ensureAsync
log
memoize
nextTick
reflect
reflectAll
setImmediate
timeout
unmemoize

Thursday, 15 June 2017

request module with nodeJs tutorial

How to post get/post request with parameter? How to send headers in ajax call.

Question: What is request module?
Request is designed to be the simplest way possible to make http/https calls.

Question: How to install request module?

npm install request

Question: How to include request module in node project?

var request = require('request');

Question: Give example of GET http call?

var request = require('request');
request('http://domain.com/ajax.php', function (err, response, body) {
   if (err) {
    return console.error('upload failed:', err);
  }
    console.log(body);  
});

Question: Give example of POST http call with parameter?

request({method:'post',url:'http://domain.com/ajax.php', form: {name:'hello',age:25},headers:options}, function (error, response, body) {  
    console.log(body);  
});

Question: How to send custom header with post method?

var headersOpt = {  
    'User-Agent': 'request'  
};
request(
        {
        method:'post',
        url:'http://domain.com/ajax.php', 
        form: {name:'hello',age:25}, 
        headers:headersOpt
    }, function (error, response, body) {  
        
        console.log(body);  
});

Question: How to set cookie with request?

request.cookie('key1=value1')

Wednesday, 14 June 2017

mocha module with nodeJs tutorial

Question: What is Mocha?
Mocha is a Rich JavaScript framework running on Node.js and in the browser making asynchronous testing simple and fun. Mocha tests run serially, allowing for flexible and accurate reporting, while mapping uncaught exceptions to the correct test cases.

Question: How to install Mocha?

npm install --global mocha

Question: How to test script with Mocha?

mocha tests.js

Question: How to check Success with Mocha?
Success

function add(a,b){
  return a+b;
}

   
//Success
it('should add two numbers-Success', () => {
  var res = add(33, 11);

  if (res !== 44) {
    throw new Error(`Expected 44, but got ${res}.`)
  }
});

Output
should add two numbers-Success passing (15ms)

Question: How to check Failure with Mocha?

function add(a,b){
  return a+b+2;
}

   
//Failed
it('should add two numbers-Success', () => {
  var res = add(33, 11);

  if (res !== 44) {
    throw new Error(`Expected 44, but got ${res}.`)
  }
});

Output
1) should add two numbers-Failed 0 passing (25ms) 1 failing 1) should add two numbers-Failed: Error: Expected 44, but got 46. at Context.it (utils\utils.test.js:11:11)

Question: How to write Asynchronous code with Mocha?

describe('User', function() {
  describe('#save()', function() {
    it('should save without error', function(done) {
      var user = new User('Luna');
      user.save(done);
    });
  });
});

Question: How to write Synchronous code with Mocha?

describe('Array', function() {
  describe('#indexOf()', function() {
    it('should return -1 when the value is not present', function() {
      [1,2,3].indexOf(5).should.equal(-1);
      [1,2,3].indexOf(0).should.equal(-1);
    });
  });
});

Question: How we can achieve HOOKS with Mocha?

describe('hooks', function() {
  before(function() { });
  after(function() {  });
  beforeEach(function() {  });
  afterEach(function() {});  
});

Question: What is Github URL for mocha?
https://github.com/mochajs/mocha

Question: In Which language mocha is written?
JavaScript

Question: What is offical website URL of Mocha?
https://mochajs.org/

Monday, 12 June 2017

Node js Redis tutorial - Quick Start

Install redis in nodeJS, Make redis connection and stored data in redis, Get data from redis, update and delete the data from redis.

Question: How to install redis module with node?

npm install redis

Question: How to include redis in nodeJS Project?

var redis = require("redis");

Question: How to connect to redis with nodeJS?

var client = redis.createClient();

//On connection
client.on('connect', function() {
    console.log('connected');
});

//On error of connection
client.on('error', function() {
    console.log('error');
});

Question: How to Store data/Get Data/ Delete data in redis with nodejs?
Store single value

client.set('technology', 'NodeJS');

Get Stored value

client.get('technology');

Delete Stored value

client.del('technology', function(err, reply) {
    console.log(reply);
});

Question: How to check Stored value exist OR Not

client.exists('technology', function(err, reply) {
    if (reply === 1) {
        console.log('Stored in Redis');
    } else {
        console.log('Not Stored in Redis');
    }
});

Question: What is HMSET in nodeJS?
HMSET is like hset but it allow to store value in "key/value" paris.

Question: How to store data in key/value pairs in redis?

client.hmset('frameworks_list', {
    'javascript': 'AngularJS',
    'css': 'Bootstrap',
    'node': 'Express'
}, function(err, msg) {
    if (err) {
        console.log("Error During save the data");
    }
    //console.log(msg);//ok    
});

Question: How to get data which was stored with hmset redis?

client.hgetall('frameworks_list', function(err, msg) {
    if (err) {
        console.log("Error During save the data");
    }
    //console.log(msg);//{javascript: 'AngularJS', css: 'Bootstrap', node: 'Express' }
});

Question: How to store unique values in redis?

client.sadd(['emails', 'abc1@no-spam.ws', 'abc2@no-spam.ws', 'abc3@no-spam.ws'], function(err, msg) {
});

Question: How to get stored values which was set sadd with in redis?

client.smembers('emails', function(err, msg) {
    
});

Thursday, 8 June 2017

How to Create RESTful APIs in Node Js using Express JS and MongoDB

Question: What is RESTful APIs?
Full form of REST is Representational State Transfer. It is web standards architecture used to create an API.

Question: What type of request handled by RESTful APIs?
HTTP requests

Question: How to create an API?

Create a folder with name of api in your node project, and create three folder inside this. i.e controllers, models and routes.
Create 3 empty files in each folder i.e todoListController.js, todoListModel.js and todoListRoutes.js
Now, Folder Structure will be as below:

-api
    --api/controllers/todoListController.js
    --api/models/todoListModel.js
    --api/routes/todoListRoutes.js

Add Following script in each empty file: todoListController.js

var mongoose = require('mongoose'),
        Task = mongoose.model('Tasks');

/* List all todoList*/
exports.list_all_tasks = function(req, res) {
    Task.find({}, function(err, task) {
        if (err)
            res.send(err);
        res.json(task);
    });
};


/* List all todoList*/
exports.create_a_task = function(req, res) {
    var saveData = {}
    saveData.name = req.body.name;
    saveData.status = req.body.status;
    var new_task = new Task(saveData);
    new_task.save(function(err, task) {
        if (err)
            res.send(err);
        res.json(task);
    });    
};

/* Get a todo list details*/
exports.read_a_task = function(req, res) {
    Task.findById(req.params.taskId, function(err, task) {
        if (err)
            res.send(err);
        res.json(task);
    });
};

/* UPdate a toto data*/
exports.update_a_task = function(req, res) {
    Task.findOneAndUpdate(req.params.taskId, req.body, {new : true}, function(err, task) {
        if (err)
            res.send(err);
        res.json(task);
    });
};


exports.delete_a_task = function(req, res) {
    Task.remove({
        _id: req.params.taskId
    }, function(err, task) {
        if (err)
            res.send(err);
        res.json({message: 'Task successfully deleted'});
    });
};

todoListModel.js

var mongoose = require('mongoose');
var Schema = mongoose.Schema;

var TaskSchema = new Schema({
    name: {
        type: String,
        Required: 'Kindly enter the name of the task'
    },
    Created_date: {
        type: Date,
        default: Date.now
    },
    status: {
        type: [{
                type: String,
                enum: ['pending', 'ongoing', 'completed']
            }],
        default: ['ongoing']
    }
});

module.exports = mongoose.model('Tasks', TaskSchema);

todoListRoutes.js

module.exports = function(app) {
    var todoList = require('../controllers/todoListController');


    // todoList Routes
    app.route('/tasks')
            .get(todoList.list_all_tasks)
            .post(todoList.create_a_task);


    app.route('/tasks/:taskId')
            .get(todoList.read_a_task)
            .post(todoList.update_a_task)
            .delete(todoList.delete_a_task);
};

Create a myapp.js empty file in project folder and add following script code.

var express = require('express'),
app = express(),
port = process.env.PORT || 3000,
mongoose = require('mongoose'),
Task = require('./api/models/todoListModel'),
bodyParser = require('body-parser');

mongoose.Promise = global.Promise;
mongoose.connect('mongodb://localhost/Tododb');

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

var routes = require('./api/routes/todoListRoutes');
routes(app);

app.listen(port);
console.log('RESTful API server started: ' + port+' PORT');

Now you need install following modules

npm install express
npm install mongoose
npm install body-parser

Now run following command, to test the APIs
```
node myapp.js
```

Question: Provide Create Task API
URL: http://localhost:3000/tasks
Method: POST
Request Data:

{
"name":"I need to go for walk",
"status":"ongoing"
}

Question: Provide List All records API
URL: http://localhost:3000/tasks
Method: POST
Response Data:

[{"_id":"5937ff6a5fc96f1c1492877f","name":"I will go for walk daily.","__v":0,"status":["ongoing"],"Created_date":"2017-06-07T13:28:10.608Z"},{"_id":"593803fb5fc96f1c14928782","name":"Get up early in the morning","__v":0,"status":["ongoing"],"Created_date":"2017-06-07T13:47:39.246Z"}]

Question: Provide Update Records
URL: http://localhost:3000/tasks/5938d8e86d3e500cd8da6a12
Method: POST
Request Data:

{  
  "name": "I goes on walk daily.", 
}

Question: Provide Get Records:
URL: http://localhost:3000/tasks/5938d8e86d3e500cd8da6a12
Method: POST
Response Data:

{"_id":"5938d8e86d3e500cd8da6a12","name":"Arun kumar Gupta","__v":0,"status":["ongoing"],"Created_date":"2017-06-08T04:56:08.156Z"}

Question: Provide Delete Records
URL: http://localhost:3000/tasks/5938d8e86d3e500cd8da6a12
Method: DELETE
Response Data:

{
  "message": "Task successfully deleted"
}

Tuesday, 6 June 2017

How to use cookies with expressJS in node.js

Question: What is cookies in NodeJS?
Cookies is a node.js module for getting and setting HTTP(S) cookies.

Question: How to install cookies?

npm install cookie-parser

Question: How to setup cookie with expressJS?

var express = require('express');
var cookieParser = require('cookie-parser');

var app = express();
app.use(cookieParser());

Question: What are the feature of cookie?

Lazy: Since cookie verification against multiple keys could be expensive, So cookies are verified lazily.
Secure: All cookies are httponly by default and cookies sent over SSL are secure by default.
Unobtrusive: Signed cookies are stored the same way as unsigned cookies, instead of in an obfuscated signing format.
Agnostic: This library is optimized for use with Keygrip, but does not require it.

Question: How to set cookies?

app.get('/set-cook', function(req, res) {
       //Set the cookie
      var c_name='cookie_name';        
      res.cookie(c_name, 'cookie value');
      
      //Send Response
      res.send('cookie value');
});

Note above wll work with expressJs only.
Question: How to get cookies?

app.get('/get-cook', function(req, res) {        
    //Get cookie name
      var cookieValue=req.cookies.cookie_name; 

      //Send Response
      res.send('Cookie name is '+cookieValue);
});

Note above wll work with expressJs only.

Question: How to delete cookies?

app.get('/delete-cook', function(req, res) {        

    //Delete the cookie
     clearCookie(cookie_name);

      //Send Response
      res.send('Cookie name is '+cookieValue);
});

Note above wll work with expressJs only.

Question: How to set expiration time for cookie?

res.cookie(name , 'value', {expire : new Date() + 600}); //10 minutes

res.cookie(name , 'value', {expire : new Date() + 3600}); //1 hour

res.cookie(name , 'value', {expire : new Date() + 18000}); //5 hour

Question: What are HTTP cookies?
HTTP cookies are small pieces of data that are sent from a website and stored in your browser. With use of cookies we maintain the login and track the user activities. Cookies are very valuable to better user experience. Following are the three main use of cookies.

Session management
Personalization
Track the user activites

Question: Why we must use Cookie-Free Domains for static contents?
Cookies are very useful in website. But while access static contents of website like CSS, image and JS then there is no use of cookie. Means while Browser is accessing the static file, Server should send the static content without use of cookie. It will improve the website performance.

Monday, 5 June 2017

Mongoose Tutorial - listing records, Add Record, update record and delete record

Question: How to install the mongoose?

npm install mongoose

Question: How to update the mongoose?

npm update mongoose

Question: How to Start the mongoose?
Include the mongoose in the project

var mongoose = require('mongoose');

Make the Db connection with mongodb

mongoose.connect('mongodb://localhost:27017/test');
var db = mongoose.connection;

Check the Error OR Success on Db Connection

db.on('error', console.error.bind(console, 'connection error:'));
db.once('open', function() {
   console.log("MongoDB connected Successfully.!");
});

Question: How to Create Model with mongoose?
Here we have set the two fields only, you can add more if required.

var TodoSchema = mongoose.Schema({
  id: String, //datatype is string
  name: String, //datatype is string          
});       
var Todo = mongoose.model('Todo', TodoSchema);

In mongoose.model, the first argument is the singular name of the collection.
Mongoose automatically looks for the plural version with lowercase of your model name.
means for Todo, it will look todos.

Question: How to set unique key for a field?

var TodoSchema = mongoose.Schema({
  id: { type: Number, unique: true}, 
  name: String, //datatype is string          
});

Question: How to set unique key and required for a field?

var TodoSchema = mongoose.Schema({
  id: { type: Number, unique: true }, 
  email: { type: String, unique: true, required:true }, 
  name: String, //datatype is string          
});

Question: How to list the records from mongodb?

var cursor = Todo.find({ }).cursor();
cursor.on('data', function(doc) {
    jsonData[doc.id] = doc.name;  
});
cursor.on('close', function() {
    console.log(jsonData);                   
});

Question: How to save the record?

var TodoDetails = new Todo({ id: "10",name:"this id test message"});
TodoDetails.save(function (err) {if (err) console.log ('Error on save!')});

Question: How to update the record?

 Todo.update({id: "10" }, { $set: { name: "this is update message" }}, {}, function(){
             console.log("Update the records successfully");
        })

Question: How to delete the record?

    Todo.find({ id:"10" }).remove( function(){
     console.log("Record deleted successfully");
    });

Question: How to delete the document and check is it deleted?

Todo.find({ id:"10" }).remove( function(err, effectedRows){
    if(err){
         console.log("Unable to delete the record");
    }
    if(effectedRows.n==0){
        console.log("Zero Record deleted");
    }else{
        console.log("Record deleted successfully");
    }
     
 });

Question: What are the difference between mongoose.model and mongoose.Schema?
Model is an object that gives you easy access to a collection, allowing you to query the collection and use the Schema to validate any documents you save to that collection. It is created by combining a Schema, a Connection, and a collection name.

Schema is an object that defines the structure of the documents that will be stored.
it enables you to define types and validators for all data.

Question: How to get first record(s) from listing?

Todo.findOne({ 'name': 'kumar' }, 'id', function (err, person) {
  if (err) return handleError(err);
    console.log(person);          

})

Question: How to fetch specific column?

  Todo.find({ 'name': 'kumar' }, 'id name', function (err, person) {
          if (err) return handleError(err);
            //console.log(person);          
             res.send(person);
        })

Question: How to limit the number of records?
You can use limit method.

Todo.find({}, 'id name', function (err, person) {
  if (err) return handleError(err);
    console.log(person);          
     
}).limit(3);

Question: How to get listing by name in ascending order?
You can use sort method, -1 means descending order, 1 means ascending order.

Todo.find({}, 'id name', function (err, person) {
  if (err) return handleError(err);
    console.log(person);          
     
}).limit(3).sort({ name: -1 });

Question: How to use "in" in where clause?

Todo.find({ name: { $in: ['arun', 'gupta']}, 'id name', function (err, person) {
  if (err) return handleError(err);
    console.log(person);          
     
}).limit(3).sort({ name: -1 });

Question: Give full Query example?

Todo.find({ 
    occupation: /host/,
    'name.last': 'Ghost',
    age: { $gt: 17, $lt: 66 },
    name: { $in: ['technology', 'web'] }

}, 'id name', function (err, person) {
  if (err) return handleError(err);
    //Here will be display all the records
    console.log(person);               
}).limit(3).sort({ name: -1 });

Question: How to create custom function in mongoose.model?
In schema/Model file (Create a custom function)

var TodoSchema = mongoose.Schema({
  id: { type: Number, unique: true}, 
  name: String, //datatype is string          
});
TodoSchema.statics.findByIdTest = function (todoId,cb) {
  return this.model('Todo').find({ id: todoId }, cb);
};

How to use controller file.

Todo.findByIdTest(2677,function(error, data){
    console.log(data);    
});

Subscribe to: Posts ( Atom )

Thursday, 29 June 2017

Best Related Posts are Following:

Wednesday, 28 June 2017

Best Related Posts are Following:

Thursday, 22 June 2017

Best Related Posts are Following:

Tuesday, 20 June 2017

Best Related Posts are Following:

Monday, 19 June 2017

Best Related Posts are Following:

Friday, 16 June 2017

Best Related Posts are Following:

Thursday, 15 June 2017

Best Related Posts are Following:

Wednesday, 14 June 2017

Monday, 12 June 2017

Best Related Posts are Following:

Thursday, 8 June 2017

Best Related Posts are Following:

Tuesday, 6 June 2017

Best Related Posts are Following:

Monday, 5 June 2017

Best Related Posts are Following: