When creating an invalid JS script and then clicking interactive view after execution, a JavaScript error window appears, saying:
"eval@[native code]
file:///var/folders/c4/68bc751d1q7cdrxkrx7plfhh0000gn/T/knimeViewContainer7470/org/knime/js/base/node/viz/generic/knime-generic-view.js:42:13"
etc.
The first weird behaviour is that this error message cannot be closed (Mac OS X latest edition) and KNIME has to be force quit for it to disappear.
The cause of it is however that the node's state is green instead of red and the Interactive view can be accessed.
the node needs to be executed and be in the 'green' state for the view to be available in general. During the execution of the view the JavaScript code is not evaluated, unless you generate an image, in which case a PhantomJS instance is started in the background and the JavaScript is executed in there as well.
It is also expected that an error window pops up on script errors. The script entered in the node's dialog is essentially wrapped in a try/catch block, which issues an alert window in case of errors.
What is strange though, is that you can't close this window. Could you provide a screenshot of the described behavior? Is it because the window is too large for the screen? Are the buttons missing on the bottom?