Q1660 Is it possible to add a property or a method to pre-built objects, such as Image objects?

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Q1660 Is it possible to add a property or a method to pre-built objects, such as Image objects?

Yes. Try the following that adds properties and methods to individual object instances:

<script language="JavaScript"><!--
function myFunction() {
   alert(this.myProperty);
}

var myImage = new Image();

myImage.myProperty = 'Hello world';

myImage.myMethod = myFunction;

myImage.myMethod();
//--></script>

I said individual object instances, as the following will fail with "myImage2.myMethod is not a function.":

<script language="JavaScript"><!--
function myFunction() {
   alert(this.myProperty);
}

var myImage = new Image();

myImage.myProperty = 'Hello world';

myImage.myMethod = myFunction;

myImage.myMethod();

var myImage2 = new Image();

myImage2.myMethod();
//--></script>

To add a property or method to the Object type such that all instance of that object type inherit the property and/or method use the prototype keyword:

<script language="JavaScript"><!--
function myFunction2() {
   alert(this.myPrototypeProperty);
}

window.Image.prototype.myPrototypeMethod = myFunction2;

window.Image.prototype.myPrototypeProperty = 'dlrow olleH';

var myImage3 = new Image();

myImage.myPrototypeMethod();
//--></script>

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