nikkaroraa/day6.txt

## day6.txt
Code @https://cb.lk/nodeintro


res.send("<html><b>hello</b></html>"); //html can be used with res.send() but not with res.write()

var express = require('express');

var app = express();

app.use('/', express.static(__dirname + '/public/'));
//statically mounting a folder or mounting static folders.
//the folder -> __dirname + '/public' is statically available on '/' route

app.get('/', function(req, res){
	res.send('Hello')
});

//when 2 requests are made to the same route, then the one that comes first, gets served.
//app.use('/', express.static(__dirname + '/public/'));
//statically mounting a folder.

app.get('/hello', function(req, res){
	res.send('Hello')
});

app.listen(2222, function(){
	console.log("Listening");
});

Refer: https://expressjs.com/en/starter/static-files.html

Static directories
The files for your pages themselves are still static. That is, you are not creating them dynamically with server-side code. What happens in the browser doesn't matter in this context... the idea is that you do not need to generate these files on the fly, as their content does not change.

Static files are files that clients download as they are from the server


query and queryString difference
https://stackoverflow.com/questions/29960764/what-does-extended-mean-in-express-4-0


The reason for this message is that body-parser is about to change default value for extended from true to false.

Extended protocol uses qs library to parse x-www-form-urlencoded data. The main advantage of qs is that it uses very powerful serialization/deserialization algorithm, capable of serializing any json-like data structure.

But web-browsers don't normally use this protocol, because x-www-form-urlencoded was designed to serialize flat html forms. Though, it may come in handy if you're going to send rich data structures using ajax.

querystring library` provides basic serialization/deserialization algorithm, the one used by all web-browsers to serialize form data. This basic algorithm is significantly simpler than extended one, but limited to flat data structures.

Both algorithms work exactly the same with flat data.

Now, when you know pros and cons of both algorithms, it's up to you to decide which one suits your application better.


var a =false;

setTimeout(function(){
	a = true;
}, 1000)

while(!a){
	console.log(a);
}


setTimeout(function(){
	a = true;
}, 1000)


uneval(Math.pow()) //written in interpreter. Native code, Already compiled code

EventLoop in JS
EventLoop keeps on executing.
If the engine is processing, then it takes blank code and returns a busy signal.

If it is not processing anything

JS is not asynchronous by itself.
There are methods that make it asynchronous.

- nextTick (available only in node JS) (process.nextTick(cb)) -> next time the event clock (the tick) is free, then call cb();
- setInterval
- setTimeout

If a function has a callback, then it doesn't mean that it is an asynchronous function.


fs.write works with file descriptor
fs.writeFile works with file names.


Error-First functions - Functions which have err as their first argument. function(err, ...){}

Buffer:
Pure JavaScript is Unicode friendly, but it is not so for binary data. While dealing with TCP streams or the file system, it's necessary to handle octet streams. Node provides Buffer class which provides instances to store raw data similar to an array of integers but corresponds to a raw memory allocation outside the V8 heap.


buf = new Buffer(26);
for (var i = 0 ; i < 26 ; i++) {
  buf[i] = i + 97;
}

console.log( buf.toString('ascii'));       // outputs: abcdefghijklmnopqrstuvwxyz
console.log( buf.toString('ascii',0,5));   // outputs: abcde
console.log( buf.toString('utf8',0,5));    // outputs: abcde
console.log( buf.toString(undefined,0,5)); // encoding defaults to 'utf8', outputs abcde

Refer: https://www.tutorialspoint.com/nodejs/nodejs_buffers.htm


Without JS:
Handlebars: Templating Engine

SQLDatabase: CRUD Operations
	Code @https://cb.lk/nodeintro


	res.send("<html><b>hello</b></html>"); //html can be used with res.send() but not with res.write()

	var express = require('express');

	var app = express();

	app.use('/', express.static(__dirname + '/public/'));
	//statically mounting a folder or mounting static folders.
	//the folder -> __dirname + '/public' is statically available on '/' route

	app.get('/', function(req, res){
	res.send('Hello')
	});

	//when 2 requests are made to the same route, then the one that comes first, gets served.
	//app.use('/', express.static(__dirname + '/public/'));
	//statically mounting a folder.

	app.get('/hello', function(req, res){
	res.send('Hello')
	});

	app.listen(2222, function(){
	console.log("Listening");
	});

	Refer: https://expressjs.com/en/starter/static-files.html

	Static directories
	The files for your pages themselves are still static. That is, you are not creating them dynamically with server-side code. What happens in the browser doesn't matter in this context... the idea is that you do not need to generate these files on the fly, as their content does not change.

	Static files are files that clients download as they are from the server


	query and queryString difference
	https://stackoverflow.com/questions/29960764/what-does-extended-mean-in-express-4-0


	The reason for this message is that body-parser is about to change default value for extended from true to false.

	Extended protocol uses qs library to parse x-www-form-urlencoded data. The main advantage of qs is that it uses very powerful serialization/deserialization algorithm, capable of serializing any json-like data structure.

	But web-browsers don't normally use this protocol, because x-www-form-urlencoded was designed to serialize flat html forms. Though, it may come in handy if you're going to send rich data structures using ajax.

	querystring library` provides basic serialization/deserialization algorithm, the one used by all web-browsers to serialize form data. This basic algorithm is significantly simpler than extended one, but limited to flat data structures.

	Both algorithms work exactly the same with flat data.

	Now, when you know pros and cons of both algorithms, it's up to you to decide which one suits your application better.


	var a =false;

	setTimeout(function(){
	a = true;
	}, 1000)

	while(!a){
	console.log(a);
	}


	setTimeout(function(){
	a = true;
	}, 1000)


	uneval(Math.pow()) //written in interpreter. Native code, Already compiled code

	EventLoop in JS
	EventLoop keeps on executing.
	If the engine is processing, then it takes blank code and returns a busy signal.

	If it is not processing anything

	JS is not asynchronous by itself.
	There are methods that make it asynchronous.

	- nextTick (available only in node JS) (process.nextTick(cb)) -> next time the event clock (the tick) is free, then call cb();
	- setInterval
	- setTimeout

	If a function has a callback, then it doesn't mean that it is an asynchronous function.


	fs.write works with file descriptor
	fs.writeFile works with file names.



	Error-First functions - Functions which have err as their first argument. function(err, ...){}

	Buffer:
	Pure JavaScript is Unicode friendly, but it is not so for binary data. While dealing with TCP streams or the file system, it's necessary to handle octet streams. Node provides Buffer class which provides instances to store raw data similar to an array of integers but corresponds to a raw memory allocation outside the V8 heap.


	buf = new Buffer(26);
	for (var i = 0 ; i < 26 ; i++) {
	buf[i] = i + 97;
	}

	console.log( buf.toString('ascii')); // outputs: abcdefghijklmnopqrstuvwxyz
	console.log( buf.toString('ascii',0,5)); // outputs: abcde
	console.log( buf.toString('utf8',0,5)); // outputs: abcde
	console.log( buf.toString(undefined,0,5)); // encoding defaults to 'utf8', outputs abcde

	Refer: https://www.tutorialspoint.com/nodejs/nodejs_buffers.htm


	Without JS:
	Handlebars: Templating Engine

	SQLDatabase: CRUD Operations