Javascript: the important bits

JAVASCRIPT: THE
IMPORTANT BITS
REVIEWING JAVASCRIPT AND JQUERY FUNDAMENTALS AS WELL AS A
BRIEF INTRO TO NODEJS

THINK YOU KNOW JAVASCRIPT?
typeof [] === "array"; false
0.1 + 0.2 === 0.3; false
a === null; false
0 == '0'; true
1 == '1'; true
'' == '0'; false
'' == 0; true
'false' == false; false

True or false?

THINK YOU KNOW JAVASCRIPT?
return
{
a: "hello"
}

What does this return?

LET'S GET STARTED WITH THE BASICS.

VARIABLES
When declairing a variable without the "var", it puts the variable in
global space which can be problematic.

function hello() {
test1 = 'hello'; // global scope
var test2 = 'hello2'; // this function scope
}

hello();

console.log(test1); // 'hello';
console.log(test2); // undefined

SCOPING
There is no block scoping, only function scoping:
for (var i = 0; i < 10; i++) {
console.log(i);
}
console.log(i); // prints 10

If you want to block the scope of the above loop:
(function () {
for (var i = 0; i < 10; i++) {
console.log(i);
}
}());
var i;
console.log(i); // undefined

SCOPE IN CALLBACKS
In callbacks, you can share variables from the parent function:
var obj = {
objValue: 'hello',
test: function() {
var self = this;
setTimeout(function() {
console.log(this.objValue); // undefined
console.log(self.objValue); // 'hello'
}, 10);
}
}

OBJECTS AND "CLASSES"
Objects are like JSON with some class aspects known as
prototypes.

OBJECTS AND "CLASSES"
An example class:

Animal = (function() {

function Animal(name) {
this.name = name;
}

Animal.prototype.move = function() {
return alert(this.name + ' moved.');
};

return Animal;

}());

IMMEDIATE EXECUTION FUNCTION
(function() {
// Your logic here
}());

This immediately executes your logic as anonymous scope.

PRIVATE PATTERN
var getCount = function() {
var count = 0;
return function() {
return ++count;
}
}
var next = getCount();
console.log(next()); // 1
console.log(next()); // 2

This pattern allows you to expose only what you want exposed.

INITIALIZATION
Variable initialization:
var value = value || 'somevalue';

Complex object initialization:
({
val1: 1,
val2: null,
init: function() {
this.val2 = 2;
return this;
}
}).init();

LET'S GO OVER JQUERY OPTIMIZATION.

SELECTOR CACHING
Bad:
$('.someclass').text('replace some text.');
$('.someclass').css('color', 'red');
$('.someclass').focus();

Good:
$('.someclass')
.text('replace some text.')
.css('color', 'red')
.focus();

SELECTOR CACHING
Caching with callbacks.
var $someotherclass = $('.someotherclass');
$('.someclass').on('click', function(e) {
$someotherclass.text('some event');
});

Caching "this":
$('.someclass').on('click', function(e)) {
$this = $(this);
$this.text('something');
$this.hide();
});

EVENT ATTACHING
When attaching events, use the "on" function.
$('a').on('click', function(e)) {
console.log('A link was clicked.');
});

What about dynamically generated links?
$(document).on('click', 'a', function(e)) {
console.log('A link was clicked.');
});

PROPERLY STOPPING EVENTS
Returning false is not always a good thing:
$('a').on('click', function(e) {
console.log('Stopping propagation.');
return false;
// Same as:
// e.preventDefault();
// e.stopPropagation();
});
$('a').on('click', function(e)) {
console.log('Another click.');
// Never gets called because of the
// return false in the above event.
});

BASIC JQUERY PLUGIN STRUCTURE
(function($) {
$.fn.myLog = function() {
return this.each(function() {
console.log($(this));
});
}
}(jQuery));

Usage:
$('p').myLog();

Nodejs is an event-driven language built on Google's V8 (in c).

It's package manager is known as npm and is now packaged with
nodejs.

NODEJS: HELLO WORLD
var http = require('http');
http.createServer(function (req, res) {
res.writeHead(200, {'Content-Type': 'text/plain'});
res.end('Hello Worldn');
}).listen(1337);
console.log('Server running on port 1337');

Source: http://nodejs.org/about/

NODEJS: DEPENDANCY MANAGEMENT
You can manage dependencies for your nodejs app in package.json:
{
"name": "sample-app",
"version": "0.0.1",
"dependencies": {
"express": "2.5.x"
}
}

This allows us to install our project dependencies with npm:
npm install

NODEJS: EXPRESS SERVER
Our hello world example in express:
var express = require('express');
app = express.createServer()
app.get('/', function(req, res) {
res.send('Hello World');
});
app.listen(1337);
console.log('Listening on port 1337');

NODEJS: CONNECT MIDDLEWARE
Routing middleware is anything that implements the request,
response, and next function pattern.
// Request logger
function logger(req, res, next) {
console.log("Path requested: " + req.path);
next();
}

Using this middleware:
app.get('/', logger, function(req, res) {
res.send('Hello World');
});

Javascript: the important bits

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Javascript: the important bits