Javascript: parent.framename.document.forms[i].elements.length

Question

I have a PHP-Script 1 with an iframe.
In this iframe an other PHP-Script 2 is loaded, which contains several forms.
In one of this forms I make a call by button with onclick="..." to a javascript-function.
The javascript-function is contained in an external file *.js. Declaration in PHP-Script 2: <Script type="text/javascript" src="WartArtikel-Probe.js"></Script>.
Inside the javascript-function I use:
Scenario 1:
var i = 0;
var anzelem = parent.framename.document.forms[i].elements.length;
or:
var anzelem = parent.frames[0].document.forms[i].elements.length;
or:
var anzelem = window.document.forms[i].elements.length;
When I press the button, the javascript-function gives no answer.
But when I start PHP-Script 2 directly (not inside an iframe) and the javascript-function is written as:
Scenario 2:
var i = 0;
var anzelem = document.forms[i].elements.length;
this example works!
How can I get an answer in scenario 1?
Additional suggestion: Is it possible to switch the browser into a development-modus, where javascript-syntax-errors are displayed? This could be very helpful!

Answer 1

To view script errors, you can keep the Browser Console open in a separate window. To open that, you can use either:
* Ctrl+Shift+j
* "3-bar" menu button > Developer > Browser Console
* Tools menu > Web Developer > Browser Console
My guess is you will find some kind of security related issue.