How can I create an object of a class which is defined in the remote page?

Question

For example, in the remote webpage, there is a snippet of code like this:

<script>
function foo(){
this.bar = 0;
}

In my greasemonkey script, I want to create an object of this class:

var _foo= unsafeWindow['foo'];
new _foo();

Then I got an Illegal Value error.

Answer 1

Here's how to do it:

var _foo = eval('(' + unsafeWindow.foo.toSource() + ')');
var x = new _foo();

This workaround may be required due to the different security zones or sandboxing that Greasemonkey does, though I'm not entirely sure.