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Asked: 2026-05-20T09:40:34+00:00

Alright, I’m trying to use the basic document.getElementsByTagName function, but each time I do,

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Alright, I’m trying to use the basic document.getElementsByTagName function, but each time I do, it brings up results that don’t exist. Ie: elements with undefined nodeNames, and things like this. This causes my script to halt, and is giving me quite the trouble.

Here is a sample:

This HTML

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
  <head>
    <title></title>
  </head>
  <body>
    <div></div>
    <div></div>
    <div></div>
  </body>
</html>

with this script

for(x in document.getElementsByTagName('div'))
  alert(document.getElementsByTagName('div')[x].nodeName);

generates this

DIV
DIV
DIV
undefined

then the script quits.

I cannot locate the issue, and it works like this in all browsers…

Just ask for any other details…

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1 Answer

  1. Editorial Team

    Correction: getElementsByTagName returns a NodeList, which has numeric indices and a length property, thereby making it an Array-like object.

    Nevertheless, you should just use a simple for loop like so:

    var els = document.getElementsByTagName('div');
for(var i = 0, j = els.length; i < j; i++) {
  alert(els[i].nodeName);

    The reason why you want to use for and not for..in here is because for..in uses inherited properties of the iterated object, so to avoid that you can use hasOwnProperty, but in this case where you’re only iterating over a numeric indice, I think it’s better to use a simple for loop over using for..in and hasOwnProperty.

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