Mega Code Archive
Using zInherit Library to build class inheritance in three levels
<![CDATA[
< html>
<head>
<title>Example</title>
<script type="text/javascript">
/*------------------------------------------------------------------------------
* JavaScript zInherit Library
* Version 1.0
* by Nicholas C. Zakas, http://www.nczonline.net/
* Copyright (c) 2004-2005 Nicholas C. Zakas. All Rights Reserved.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation; either version 2.1 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*------------------------------------------------------------------------------
*/
/**
* Inherits properties and methods from the given class.
* @scope public
* @param fnClass The constructor function to inherit from.
*/
Object.prototype.inheritFrom = function (fnClass /*: Function */) /*:void*/ {
/**
* Inherits all classes going up the inheritance chain recursively.
* @param fnClass The class to inherit from.
* @param arrClasses The array of classes to build up.
* @scope private
*/
function inheritClasses(fnClass /*:Function*/,
arrClasses /*:Array*/) /*:void*/ {
arrClasses.push(fnClass);
if (typeof fnClass.__superclasses__ == "object") {
for (var i=0; i < fnClass.__superclasses__.length; i++){
inheritClasses(fnClass.__superclasses__[i], arrClasses);
}
}
}
if (typeof this.constructor.__superclasses__ == "undefined") {
this.constructor.__superclasses__ = new Array();
}
inheritClasses(fnClass, this.constructor.__superclasses__);
for (prop in fnClass.prototype) {
if (typeof fnClass.prototype[prop] == "function") {
this[prop] = fnClass.prototype[prop];
}
}
};
/**
* Determines if the given object is an instance of a given class.
* This method is necessary because using {@link #inheritFrom} renders
* the JavaScript <code>instanceof</code> operator useless.
* @param fnClass The constructor function to test.
* @return True if the object is an instance of the class, false if not.
* @scope public
*/
Object.prototype.instanceOf = function (fnClass /*:Function*/) /*: boolean */ {
if (this.constructor == fnClass) {
return true;
} else if (typeof this.constructor.__superclasses__ == "object") {
for (var i=0; i < this.constructor.__superclasses__.length; i++) {
if (this.constructor.__superclasses__[i] == fnClass) {
return true;
}
}
return false;
} else {
return false;
}
};
</script>
</head>
<body>
<script type="text/javascript">
function Shape(iSides) {
this.sides = iSides;
}
Shape.prototype.getArea = function () {
return 0;
};
function Triangle(iBase, iHeight) {
Shape.call(this, 3);
this.base = iBase;
this.height = iHeight;
}
Triangle.prototype.inheritFrom(Shape);
Triangle.prototype.getArea = function () {
return 0.5 * this.base * this.height;
};
function Rectangle(iLength, iWidth) {
Shape.call(this, 4);
this.length = iLength;
this.width = iWidth;
}
Rectangle.prototype.inheritFrom(Shape);
Rectangle.prototype.getArea = function () {
return this.length * this.width;
};
var triangle = new Triangle(12, 4);
var rectangle = new Rectangle(22, 10);
alert(triangle.sides);
alert(triangle.getArea());
alert(rectangle.sides);
alert(rectangle.getArea());
alert(triangle.instanceOf(Triangle));
alert(triangle.instanceOf(Shape));
alert(rectangle.instanceOf(Rectangle));
alert(rectangle.instanceOf(Shape));
</script>
</body>
</html>
]]>