getRangeAt() -- error if no text is selected

Question

I use this simple Javascript code to retrieve text that was selected on a webpage:

var userselection = window.getSelection(); //user selection will be a Selection-Object
var rangeObject = userselection.getRangeAt(0); 

The code works fine if text is selected. If I just click in the text that could be selected I get a range object too, it is collapsed as expected.

But if I don't select nor click, Firefox throws this error:

uncaught exception: [Exception... "Component returned failure code: 0x80070057
(NS_ERROR_ILLEGAL_VALUE)  [nsISelection.getRangeAt]" nsresult: "0x80070057 
(NS_ERROR_ILLEGAL_VALUE)" location: "JS frame :: file:///home/jan/Webprojekte/test-range
selection.html# :: who :: line 16" data: no]

Is there a clean way to prevent the error but still notificate the user that no text was selected?

Answer 1

Yes: check the selection's rangeCount property first. If it's zero, don't call getRangeAt().