JavaScript provides core functionality for web pages and applications. It has a C-like syntax and is dynamically typed. JavaScript code runs on both the client-side in web browsers and the server-side in environments like Node.js. It uses prototype-based inheritance where objects can inherit properties from object prototypes. New features are being added regularly through the ECMAScript specification. JavaScript allows DOM manipulation to modify web pages and event handling for user interactions.

1. JavaScript
Core
Nicolas Demengel and François Sarradin

2. Application
(client side) Web Page
Animation
HTLM(5)
CSS(3)
Client
JavaScript Server
JS
Engine
Service
(server side) Embeded
(noSql, ...)

3. JavaScript
History
1996 1998
1995 1997 2000 2010 What's next?
ECMA 1.3
1.0, 1.1 1.5 1.8.5 ES 6
ES 3 ES 5 Harmony
ECMAScript
Brendan Eich 1.2
@ Netscape
JavaScript

4. JavaScript
Is made of...
Self Python Perl C/Java
JavaScript
ActionScript Dart CoffeeScript

5. JavaScript
Language
&
Concepts

6. JavaScript Syntax
Looks like Java / C++
/* Factorial of n. */
function fact(n) {
// result of fact
var result = 1;
for (var i = 1; i <= n; i++) {
result *= i;
}
return result;
}

7. JavaScript
Is dynamically typed
var x = 1; // it should be an int
var s = "a"; // string or char?
// it's a function, (type of p?
// does it return something?)
function f(p) { /* ... */ }
var g; // anything (even a function)

8. JavaScript
Has bad parts
42 == '42' !== 42
if (false) <-> if (null) <-> if (undefined)
false != null == undefined
false !== null !== undefined
return
{
prop: "val"
};
Use an editor providing validation with JSLint

9. JavaScript
Has few built-in types
● Boolean true / false
● Number 42 21.6 NaN +∞ -∞
● String "hi" 'hello'
● Date java-like
● Regexp /^.*([0-9]+)w{2,3}$/
● Object {prop: val}
● Array [a, b] (it's just an Object)
● Function function() {}
● List, Map, Set: where are you? => ES 6

10. JavaScript
Can define functions
// function declaration (statement)
function f(x) { /* ... */ }
// function expression (operator)
var f = function(x) { /* ... */ };
// Function constructor
var f = new Function('x', '...');

11. JavaScript
CAN HAZ FUNCTIONZ EVERYWHERE
function compose(f, g) {
// BTW, this is a closure!
// more on that later
return function(x) {
return f(g(x));
};
}
compose(square, add_one)(10);

12. JavaScript
Function: scope & binding
var o = {
name: "an object",
logName: function() { log(this.name); }
};
// o.logName can be assigned to a variable:
var logN = o.logName;
logN();
// another way to give o the logName method
function ln() { log(this.name); }
var o = { name: "an object" };
o.logName = ln;

13. JavaScript
Function: scope & binding
// what is the value of 'this'?
var o = { /* ... */
logName: function() { log(this.name); }
};
// here it obviously refers to o
o.logName();
// what about the following?
function ln() { log(this.name); }
ln(); // er...

14. JavaScript
Function: scope & binding
● this = object to wich the function is bound
○ By default: the global object (window in browsers)
● Change the way a function is bound to an
object: apply or call

15. JavaScript
Function: scope & binding
var o = { nm: "John Doe" };
function say(message) {
console.log(this.nm + ": " + message);
}
say("hello!"); // ": hello!" (this.nm is undefined)
o.sayIt = say;
o.sayIt("greetings!"); // "John Doe: greetings!"
say.call(o, "yo!"); // "John Doe: yo!"
say.apply(o, ["hi!"]); // "John Doe: hi!"

16. JavaScript
Function arguments
(function(x, y) {
console.log(y); > 'b'
console.log(arguments.length); > 3
console.log(arguments[2]); > 'c'
console.log(arguments.callee);> function(){ }
console.log(arguments.join); > undefined
// Array.prototype.join.call(arguments)
})('a', 'b', 'c');

17. Prototype-oriented programming
Languages
Self
NewtonScript JavaScript Lua Io
Ioke
JVM

18. Prototype-oriented programming
Instance, prototype, and inheritance
var Vehicle = {
description: "some vehicle",
startEngine: function() {
console.log(this.description
+ " => engine started");
}
};
// uses Vehicle as proto
var Car = Object.create(Vehicle);
Car.description = "some car";
Car.wheelCount = 4;

19. Prototype-oriented programming
What do you get?
Vehicle.startEngine();
> "some vehicle => engine started"
Car.startEngine();
> "some car => engine started"
console.log(Vehicle.wheelCount);
> undefined
console.log(Car.wheelCount);
> 4

20. Prototype-oriented programming
Inheritance manipulation
Car.startEngine = function() {
console.log("overridden");
}
Car.startEngine(); > "overridden"
// let's delete the car-specific method
delete Car.startEngine;
// parent method is still there
Car.startEngine(); > "some car => engine started"
JS prototype-based programming
= delegation (object ⇒ prototype)

21. Prototype-oriented programming
Inheritance: level 2
Car.startEngine = function() {
Vehicle.startEngine.call(this); // ≃ super.start
console.log("model: " + this.model);
}
// inheritance is not limited to one level
var myPigeot = Object.create(Car);
myPigeot.description = "My Pigeot";
myPigeot.model = "403";
myPigeot.startEngine();
// My Pigeot: engine started
// model: 403

22. Prototype-oriented programming
Classes in JS?
Vehicule
Car
myPigeot
Vehicle, Car = prototypes ≃ classes
Note: myPigeot can be prototype too!

23. Prototype-oriented programming
Wait!...
What about that Object.create()?

24. Prototype-oriented programming
Create an instance
// Object.create(): JS 1.8.5 and +
if (!Object.create) {
Object.create = function(o) {
// creates new temp. constructor
function F() {}
// gives it o as prototype
F.prototype = o;
// instantiates
return new F();
};
}

25. Prototype-oriented programming
Classes in JS
// previous example could have been written:
var Vehicle = { /* desc, startEngine */ };
function Car(desc) { this.description = desc; }
Car.prototype = Vehicle;
Car.prototype.description = "some car";
Car.prototype.wheelCount = 4;
var myPigeot = new Car("My Pigeot");
myPigeot.model = "403";

26. Prototype-oriented programming
New in JS
Er... Car is a functions, but I can new it?!
● new is a keyword that
1. Allocates an object
2. Inits this object with constructor
● new Car("some car") is equivalent to
var car = {};
car.__proto__ = Car.prototype;
Car.call(car, "some car");

27. Prototype-oriented programming
Last word about constructor functions
What happens when calling the Car
constructor without new?
this is bound to global object
Want to play this game?
○ Change window.location and you'll risk a crash

28. Prototype-oriented programming
Last but not least
● Be carefull with this and new
● Factory method instead of new
function createCar(d) { return new Car(d); }
● Prevent bad usage of your constructor
function Car(desc) {
if (!(this instanceof Car)) {
return new Car(desc);
}
/* ... */
}

29. Prototype-oriented programming
Private members
var Entity = (function() { // class lvl
var counter = 0; // private
return function() { // instance lvl
var id = counter++; // private
this.getId = function() {
return id;
}
};
})();

30. Prototype-oriented programming
Private members
var o1 = new Entity();
var o2 = new Entity();
console.log(o1.id);
> undefined
console.log(o1.getId());
> 1
console.log(o2.getId());
> 2

31. Access to Your Web Page
DOM manipulation
DOM != JS, it's another API
No need for jQuery
○ getElementById()
○ getElementByTagName()
○ getElementByName()
○ getElementByClassName() // !IE
○ querySelector() // IE 8
○ querySelectorAll() // IE 8

32. Access to Your Web Page
DOM manipulation: tips
● know your CSS selectors
○ #element
○ .element
○ [attribute=value]
● limit changes to the DOM
○ use fragments

33. The Good, The Bad, and The Ugly

34. References
Books
David Flanagan, JavaScript: The Definitive Guide, 6th
Edition, O'Reilly Media, April 2011
Doug Crockford, JavaScript: The Good Parts, O'Reilly
Media, May 2008

35. References
Online
Doug Crockford, JavaScript: The Good Parts
http://googlecode.blogspot.com/2009/03/doug-crockford-
javascript-good-parts.html
Alex Russel, Learning to Love JavaScript
http://www.google.com/events/io/2011/sessions/learning-to-
love-javascript.html
John Resig, Learning Advanced JavaScript
http://ejohn.org/apps/learn/
Mozilla, JavaScript Reference
https://developer.mozilla.org/en/JavaScript/Reference/