09/06/2011
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L'auteur ?crit cet article JavaScript tutorial pour Flash ActionScript d?veloppeurs qui ont le m?me int?r?t - comme , travailler avec Flash et ActionScript que vous voulez toujours apprendre de nouvelles choses dans le langage de programmation JavaScript
Programmeurs ActionScript, mais il est aussi un tr?s bon tutoriel pour qui apprendre la programmation orient?e objet JavaScript Cette guides article JavaScript tutorial vous apprend ? construire un plein rempli objet JavaScript avec les m?thodes getter et setter S'il vous pla?t visitez pour plus de d?tails
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Anyway, there are (ofcourse) some techniques to code like Actionscript in JavaScript. These snippets have helped me to understand object oriented JavaScript. For too long I did not even tried to learn what was possible with JavaScript because I thought it was a very limited language. Maybe some information is outdated; I am still learning, so please share your feedback.
Object oriented javascript
In javascript it is possible to create classes, public and private vars, getters/setters and there are even constructors. A function could be seen as a class. This is a bit strange at first, but if you use it for a while you will understand. Now lets create our own class right now.
Lets port some stuff of this Color Class to javascript. It has private vars and public functions.
Declare classes
Defining classes is as easy as defining functions, because it is almost the same. After creating an function, you could already make some instances of it. The example below creates a Color class with a public variable called value. After that we create 2 instances of the Color class with some other values.
Note: I use the same code conventions as Actionscript: Classes should be UpperCased, functions/vars should be lowerCased and constants should be FULL_CAPS. Oh and since javascript looks like as1.0, I sometimes use an underscore before private vars
{
this.value = value || 0;
alert("Color created with value: " + value)
}
var myRedColor = new Color(0xFF0000); // create instance of Color (a red one)
var myOrangeColor = new Color(0xFFCC00); // create instance of Color (an orange one)
alert( myRedColor.value );
alert( myOrangeColor.value );
Public Private
In actionscript it is very useful to use encapsulation, which is a mechanism for restricting access to other objects. The previous+following example should work in all browsers. The difference between public and private vars/functions in javascript can be declared like this:
{
// public variable
this.value = value || 0xFFFFFF; // set default value to 0xFFFFFF for parameter if it isn�t defined
// private variable
var _name = "test";
// public function
this.getRandomColor = function( )
{
return Math.random() * 0xFFFFFF;
}
// private function
function getNiceColor()
{
return 0xffcc00;
}
}
// create instance of Color
var color = new Color(0xFF0000);
alert( color.value ); // returns red color
alert( color.getRandomColor() ); // returns random color
// not possible :
alert( color.getNiceColor() ); error in console; property does not exist, because function is private.
alert( color._name ); // error in console; property does not exist, because variable is private.
I think with this principles (maybe in combination with namespaces, see below) you can create clean javascript code.
Packages Namespaces
Now before using classes in javascript I had some conflicts with function and variable names because there were unwanted duplicates. I have written a little helper tool to use namespaces. It helps to prevent those conflicts. Now it looks more like Actionscript 3, only there is no such thing like �imports�. This snippet works in all browsers.
function Namespace(namespace)
{
var parts = namespace.split(".");
var root = window;
for(var i = 0; i < parts.length; i++)
{
if(typeof root[parts[i]] == "undefined")
{
root[parts[i]] = {};
}
root = root[parts[i]];
}
}
// creating my own namespace here
Namespace("nl.stroep.utils");
nl.stroep.utils.Color = function(value) // create class inside package
{
this.value = value || 0xFFFFFF;
}
var myRedColor = new nl.stroep.utils.Color(0xff0000);
alert(myRedColor.value);
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09/06/2011
L'auteur ?crit cet article JavaScript tutorial pour ...JavaScript utiles Tutoriel pour ActionScript 3 d?veloppeurs - JavaScript utiles Tutoriel pour ActionScript 3 d?veloppeurs
