=> [1] hellow world <=
Include Modules : => include a module, use the require() function with the name of the module: var http = require('http');
res.send() : => Sending a response can be achieved by calling the res.send() method. The signature of this method looks like this: res.send([body]) where the body can be any of the following: Buffer, String, an Object and an Array. This method automatically sets the Content-Type response header as well based on the argument passed to the send() method, so for example if the [body] is a Buffer the Content-Type will be set to application/octet-stream unless of course we programmatically set it to be something else.
res.end() : => There's a response and once we have collected the data or did something else we want to present that to the caller and as a last step we should end the session - this could be achieved by calling res.end().
res.write() : =>If this method is called and response.writeHead() has not been called, it will switch to implicit header mode and flush the implicit headers. This sends a chunk of the response body. This method may be called multiple times to provide successive parts of the body. Note that in the http module, the response body is omitted when the request is a HEAD request. Similarly, the 204 and 304 responses must not include a message body.
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=> [2] Create Modules <=
module.exports or exports :
=>The module.exports or exports is a special object which is included in every JS file in the Node.js application by default. module is a variable that represents current module and exports is an object that will be exposed as a module. So, whatever you assign to module.exports or exports, will be exposed as a module.
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=> [3] Core Modules <=
Core Module Description :
http:
=> http module includes classes, methods and events to create Node.js http server.
url :
=> url module includes methods for URL resolution and parsing.
querystring:
=> querystring module includes methods to deal with query string.
path :
=> path module includes methods to deal with file paths.
fs :
=> fs module includes classes, methods, and events to work with file I/O.
util :
=> util module includes utility functions useful for programmers.
HTTP Properties and Methods:
Method Description:
createClient() :
=> Deprecated. Creates a HTTP client
createServer():
=> Creates an HTTP server
get():
=> Sets the method to GET, and returns an object containing the user's request
globalAgent :
=> Returns the HTTP Agent
request():
Util Module :
=> The Util module provides access to some utility functions.
Method & Description:
debuglog() Writes debug messages to the error object deprecate() Marks the specified function as deprecated format() Formats the specified string, using the specified arguments inherits() Inherits methods from one function into another inspect() Inspects the specified object and returns the object as a string
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=> [4] Url Modules <=
URL Module : => The URL module splits up a web address into readable parts. like , host , pathname , search ,parameters url.parse(): => method, and it will return a URL object with each part of the address as properties
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=> [5] NPM <=
NPM : => NPM is a package manager for Node.js packages, or modules
Package : => A package in Node.js contains all the files you need for a module. Modules are JavaScript libraries you can include in your project.
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=> [6] UPlOAD FILES <=
Formidable Module : => There is a very good module for working with file uploads, called "Formidable".
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=> [7] Send an Email <=
Nodemailer Module: => The Nodemailer module makes it easy to send emails from your computer.
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=> [8] Express Framework <=
Express : => Express is a minimal and flexible Node.js web application framework that provides a robust set of features to develop web and mobile applications. It facilitates the rapid development of Node based Web applications. Following are some of the core features of Express framework − => Allows to set up middlewares to respond to HTTP Requests. => Defines a routing table which is used to perform different actions based on HTTP Method and URL. => Allows to dynamically render HTML Pages based on passing arguments to templates.
Request & Response :
Express application uses a callback function whose parameters are request and response objects.
app.get('/', function (req, res) { // -- })
Request Object :
=> The request object represents the HTTP request and has properties for the request query string, parameters, body, HTTP headers, and so on. Response Object :
=> The response object represents the HTTP response that an Express app sends when it gets an HTTP request.
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=> [9] Routing <=
We have seen a basic application which serves HTTP request for the homepage. Routing refers to determining how an application responds to a client request to a particular endpoint, which is a URI (or path) and a specific HTTP request method (GET, POST, and so on).
ex: => app.Method(path,Handler)
app.get('/', function (req, res) { // -- })
app.post('/', function (req, res) { // -- })
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=> [10]Path Module <=
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=> [11]Serve Static Method <=
Serve Static Method:
Static files are files that clients download as they are from the server. Create a new directory, public. Express, by default does not allow you to serve static files. You need to enable it using the following built-in middleware.
app.use(express.static('public')); Note − Express looks up the files relative to the static directory, so the name of the static directory is not part of the URL.
Note that the root route is now set to your public dir, so all static files you load will be considering public as root. To test that this is working fine, add any image file in your new public dir and change its name to "testimage.jpg". In your views, create a new view and include this file like −
html head body h3 Testing static file serving: img(src = "/testimage.jpg", alt = "Testing Image
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=> [12]url Binding <=
We can now define routes, but those are static or fixed. To use the dynamic routes, we SHOULD provide different types of routes. Using dynamic routes allows us to pass parameters and process based on them.
Here is an example of a dynamic route −
var express = require('express'); var app = express();
app.get('/:id', function(req, res){ res.send('The id you specified is ' + req.params.id); }); app.listen(3000); To test this go to http://localhost:3000/123. The following response will be displayed.
URL Building 1 You can replace '123' in the URL with anything else and the change will reflect in the response. A more complex example of the above is −
var express = require('express'); var app = express();
app.get('/things/:name/:id', function(req, res) { res.send('id: ' + req.params.id + ' and name: ' + req.params.name); }); app.listen(3000); To test the above code, go to http://localhost:3000
URL Building 2 You can use the req.params object to access all the parameters you pass in the url. Note that the above 2 are different paths. They will never overlap. Also if you want to execute code when you get '/things' then you need to define it separately.
=> [13] Middleware <=
Middleware : => Middleware functions are functions that have access to the request object (req), the response object (res), and the next middleware function in the application’s request-response cycle. These functions are used to modify req and res objects for tasks like parsing request bodies, adding response headers, etc.
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=> [14] Templating <=
Pug is a templating engine for Express. Templating engines are used to remove the cluttering of our server code with HTML, concatenating strings wildly to existing HTML templates. Pug is a very powerful templating engine which has a variety of features including filters, includes, inheritance, interpolation, etc. There is a lot of ground to cover on this.
To use Pug with Express, we need to install it,
npm install --save pug
Now that Pug is installed, set it as the templating engine for your app. You don't need to 'require' it. Add the following code to your index.js file.
app.set('view engine', 'pug'); app.set('views','./views'); Now create a new directory called views. Inside that create a file called first_view.pug, and enter the following data in it.
doctype html html head title = "Hello Pug" body p.greetings#people Hello World! To run this page, add the following route to your app −
app.get('/first_template', function(req, res){ res.render('first_view'); });
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=> [15] Post data <=
Forms are an integral part of the web. Almost every website we visit offers us forms that submit or fetch some information for us. To get started with forms, we will first install the body-parser(for parsing JSON and url-encoded data) and multer(for parsing multipart/form data) middleware.
To install the body-parser and multer, go to your terminal and use −
npm install --save body-parser multer Replace your index.js file contents with the following code −
var express = require('express'); var bodyParser = require('body-parser'); var multer = require('multer'); var upload = multer(); var app = express();
app.get('/', function(req, res){ res.render('form'); });
app.set('view engine', 'pug'); app.set('views', './views');
// for parsing application/json app.use(bodyParser.json());
// for parsing application/xwww- app.use(bodyParser.urlencoded({ extended: true })); //form-urlencoded
// for parsing multipart/form-data app.use(upload.array()); app.use(express.static('public'));
app.post('/', function(req, res){ console.log(req.body); res.send("recieved your request!"); }); app.listen(3000); After importing the body parser and multer, we will use the body-parser for parsing json and x-www-form-urlencoded header requests, while we will use multer for parsing multipart/form-data.
Let us create an html form to test this out. Create a new view called form.pug with the following code −
html html head title Form Tester body form(action = "/", method = "POST") div label(for = "say") Say: input(name = "say" value = "Hi") br div label(for = "to") To: input(name = "to" value = "Express forms") br button(type = "submit") Send my greetings