What could cause window.open to return "undefined"?

Question

I have the following script in my Xul application:

MyClass = function() {
 this.go = function() {
  try {
   var scanWindow = window.open('chrome://test/content/scanWindow.xul','Scan','chrome, width=850, height=150, centerscreen');
   dump("scanWindow = " + scanWindow); // console output in Xul
  } catch(err) {
   dump("ERROR: " + err); // console output in Xul
  }
    }
}

when i call this method it prints

scanWindow = undefined

Any hint on what might be causing this?

Answer 1

Found: what could cause this behavior is to overwrite the window.open method and return nothing. How it was done in another part of this code.

Answer 2

I do not think you can open spaces in the third argument.

Wrong:

var scanWindow = window.open('chrome://test/content/scanWindow.xul','Scan','**chrome, width=850, height=150, centerscreen**');

Correctly:

var scanWindow = window.open('chrome://test/content/scanWindow.xul','Scan','**chrome,width=850,height=150,centerscreen**');

Answer 3

var goWindow = window.open('chrome://test/content/go.xul','Go','chrome, width=850, height=150, centerscreen');
dump("scanWindow = " + scanWindow); // console output in Xul    

your dump call should be

dump("scanWindow = " + goWindow); // console output in Xul