Question

I’m making a bookmarklet, but I’ve encountered some wierd behaviour in IE8. The code causing the problem is this:

var els = document.getElementById("my_id").getElementsByTagName("*");
for(var i in els)
{
    alert(i+","+els[i])
}

The first thing that is alerted is "length, n". This isn’t the case in chrome: just in IE8.

Interestingly, it seems to behave differently depending on whether the code goes in the console/address bar or the page itself.

Is this standard behaviour?

EDIT:

Not down to the website that I run it on either. Is it possible that getElementsByTagName returns an array with a "length" key set in IE? It certainly doesn’t return a pure array.

Answer 1

What you get is not an array, it is a nodeList.
See here, click the link “getElementsByTagName(‘element_name’)”

Furthermore, for..in is not meant to be used for iterating over an array anyway. Use

var item;
for (var idx=0, len=arr.length; idx<len; ++idx) {
  item = arr[idx];
  // whatever
}

for array iteration.

For a nodelist, you can get the element with

list.item(idx); // where list is what you got from getElementsByTagName

if you want to do it “right”.