09/06/2011
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The author writes this JavaScript article tutorial for Flash ActionScript developers that have the same interest - like, work with Flash and ActionScript but still want to learn some things new in JavaScript programming language.
Although this JavaScript article tutorial is written for ActionScript programmers, but it is also a very good tutorial for who to learn object-oriented JavaScript programming. This JavaScript article tutorial guides you how to build a full-completed JavaScript object with the getter and setter methods. Please visit for more details.
Other related JavaScript OOP article tutorials:
- JavaScript OOP Tutorial for Dummies
- Pointers in OOP JavaScript
- OOP in JavaScript: Some Basics
- OOP JavaScript: Public and Private Methods
- Basic OOP Concepts in Javascript
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Getters and Setters
Now it is possible to use getters and setters. Ofcourse is does not work in IE, so this is pointless but also a bit cool to see how far we could go. Anyway there are 2 ways to define them. Read more about it here. I think the __defineGetter__ way is better; it looks ugly but you still have access to private objects.
Take a look at this getter/setter declaration example. It�s not as clean as AS3 getters/setters but it works like a charm in my browser.
{
/* public getter */
this.__defineGetter__("value", function()
{
alert("getter called; current value: " +value);
return value;
});
/* public setter */
this.__defineSetter__("value", function(val)
{
alert("setter called; new value: " +val);
value = val;
});
// public variable. For a strange reason I have to put this below the get/set definition.
this.value = value || 0xFFFFFF;
}
// create instance of Color
var color = new Color(0xFF0000);
color.value; // getter
color.value = 0xff0000; // setter
Constants
Javascript has a const too, you could use it instead of var. Ofcourse this is not implemented in IE, so it is also pretty pointless to use.
Mix them all
Now lets use namespaces, getters/setters and private/public variables and functions together.
This is a simplified ported version of this Color Class.
With this class you can modify the red,green and blue channels of a
color individually. In the original class it is possible to
lighten/darken the color too, but for this post I left these functions,
because this only illustrates the possibilities of nice OO javascript.
nl.stroep.utils.Color = function( color )
{
/* PUBLIC FUNCTIONS */
this.grayscale = function( val )
{
val = val || 0;
if (val < 0){ val = 0 }
if (val > 255) { val = 255 }
return (val << 16) | (val << | val;
}
/* PRIVATE FUNCTIONS */
function limit( val, lowerLimit, upperLimit )
{
if (val < lowerLimit){ return lowerLimit }
if (val > upperLimit) { return upperLimit }
return val;
}
/* PUBLIC GETTER FUNCTIONS */
this.__defineGetter__("value", function()
{
return (_red << 16) | (_green << | _blue;
})
this.__defineGetter__("red", function()
{
return _red;
})
this.__defineGetter__("green", function()
{
return _green;
})
this.__defineGetter__("blue", function()
{
return _blue;
})
/* PUBLIC SETTER FUNCTIONS */
this.__defineSetter__("value", function(val)
{
_red = val >> 16 & 0xFF; // red
_green = val >> 8 & 0xFF; // green
_blue = val & 0xFF; // blue
_value = val;
})
this.__defineSetter__("red", function(val)
{
_red = val;
_red = limit( _red, 0, 255 );
})
this.__defineSetter__("green", function(val)
{
_green = val;
_green = limit( _green, 0, 255 );
})
this.__defineSetter__("blue", function(val)
{
_blue = val;
_blue = limit( _blue, 0, 255 );
})
/* PRIVATE VARIABLES */
var _value = color;
var _red;
var _green;
var _blue;
/* PUBLIC VARIABLES */
this.value = _value;
};
With this javascript class, you could use it like this:
color.green = 0; // remove green.. now it is red..
color.blue = 255; // add some blue.. now it is purple..
alert(color.value.toString(16)) // alerts FF00FF and that is purple.
Hope you enjoyed this article. Feel free to share or comment.
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Mark Knol [more]
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09/06/2011
The author writes this JavaScript article tutorial for ...Helpful JavaScript Tutorial for ActionScript 3 Developers - Helpful JavaScript Tutorial for ActionScript 3 Developers - Language: English
