ADF Javascript problem: cannot get id of an component

Question

hi, am currently reading and executing examples from ADF faces Web UI Developers Guide for jdeveloper 11g.
i am trying to execute example 3-7
I have a <af:commandButton> component , whose id i want to display in an alert box.
However i am unable to display it
here is the sample code i made up:
<f:view>
<af:document title="hello from component" >
<af:form >
<af:commandButton text="show id" id="cmdbutton">
<af:clientListener method="sayHello" type="action"/>
</af:commandButton>
</af:form>
<f:facet name="metaContainer">
<trh:script>
<f:verbatim>
function sayHello(actionEvent)
var component= actionEvent.getSource();
//Get the ID for the component
var id = component.getId ;
alert("Hello from " + id);
</f:verbatim>
</trh:script>
</f:facet>
</af:document>
</f:view>
Problem 1: when i run it, the alert box displays: Hello from undefined . i was expecting Hello from cmdButton
Problem 2: in the line var id = component.getId, if i modify it as var id = component.getId() (just added the parentheses after method getId)
no alert box is displayed. in javascript when a method accepts no parameters, its ok to call it with or without parentheses. why no alert
box displayed when i add parentheses to getId.

Answer 1

in javascript calling a method with or without parentheses is OK , then why the alert box in one case and no alert box in another?
Because your assumption is wrong. Calling a function can only be done with the parenthesis. When you're not using them then you get a pointer on the function. For example:
MyNamespace = new Object();
MyNamespace.myUtilFunction = function()
    return "Hello world";
alert(MyNamespace.myUtilFunction);
alert(MyNamespace.myUtilFunction());The first alert will show something like
"function()
return "Hello world";
While the second will print "Hello world". Furthermore, if a function does not exists, like "MyNamespace.myUnexistingFunction" then the first alert would show "undefined" while the second would never even pop as there would be an "MyNamespace.myUnexistingFunction is undefined" error. Consequently, if the alert is not showing with the parenthesis then I guess getId is not a valid function on UIComponent which is possible, I assumed there would be one because there's an id property, but then again, that id would not be very useful on the client side compared to the client id.
Regards,
~ Simon