How to use prototype to extend a class / object?

Classic Servoy
1

I want to extend the JSDataSet class (object) with prototype to define a function append ( jsDataSet ). How can I realize that?

2

Here is an example with the built in Error class.

function MyError(message){
    this.message = message;
}

MyError.prototype = new Error();

Then later…

throw new MyError("Hello world!");
3

Thanks, Scott!

4

goldcougar:
Here is an example with the built in Error class.

function MyError(message){

this.message = message;

}

MyError.prototype = new Error();

If I try:

MyError.prototype.getMyErrorMessage = function () {
	return this.message;
}

I get this: “The property getMyErrorMessage is undefined for the javascript type Object” warning and if I create an object like:

var myErr = new MyError('my error' );

and call the method:

myErr.getMyErrorMessage();

I get the following error:

=>forms.boss_char_charterfaktura_base_dtl.myErr.getMyErrorMessage();
org.mozilla.javascript.EcmaError: TypeError: Cannot find function getMyErrorMessage in object [object Object]. (internal_anon#1)

How can I add my own functions / properties to the MyError ‘class’?

5

what is the full js file that you do when you do this:

MyError.prototype.getMyErrorMessage = function () {
   return this.message;
}

it must me something like this;

var initializer = function() {
  MyError.prototype.getMyErrorMessage = function () {
   return this.message;
}
}();

function MyError(message){
    this.message = message;
}

function tst() {
   var x = new MyError("test");
   x.getMyErrorMessage ();
}