That’s what I was getting last night while I was creating some simple navigation tabs. It was frustrating because it worked in Firefox and Safari, but not IE6. And the error message? Object Error? What does that tell me? Nothing!

So I narrowed down my javascript code to this line:

var tab_1 = document.getElementById("first_tab");

tab_1.removeClassName("active");

This was throwing the error. But why?

Well, it turns out in order to use the Prototype method removeClassName(), the element (in this case, tab_1) must have Prototype DOM extensions.

So how do you get elements with Prototype DOM extensions? Use the dollar method my friend.

Instead of getting the element from getElementById() and then calling removeClassName(), simply do:

$("first_tab").removeClassName("active")

And voila, it works in Firefox, Safari, and IE6.

Suppose I have a div with id = “test” and I have a controller function that removes the div using

page[:test].remove

Now suppose I have a functional test as such:

assert_select_rjs :remove, "test"

Well, it happens to be so that this test fails, even though all my other assert_select_rjs assertions succeed. Only when the first argument is :remove does the test fail.

Now I don’t know why this is (anybody want to enlighten me?), but I’ve found a workaround.

Instead of the the code above, do:

assert_equal @response.body, '$("test").remove();'

The assert_select_rjs function supposedly does a similar thing under the hood where it does a regex comparison on the response body.

And there you have it. Test success!