thead = new Array();
alert(thead.length);
thead = document.getElementsByTagName("th");
alert(thead.length);


thead.pop();
alert(thead.length);

document.getElementsByTagName("th") returns an array of elements, so thead variable should be an array, if so, then why it gives me the error "thead.pop() is not a function"?

thead = new Array();
alert(thead.length);
thead = document.getElementsByTagName("th");
alert(thead.length);


thead.pop();
alert(thead.length);

document.getElementsByTagName("th") returns an array of elements, so thead variable should be an array, if so, then why it gives me the error "thead.pop() is not a function"?

• javascript
• arrays
• function

• Are you trying to remove from the DOM, or just from the list? If you actually want it removed from the DOM, do this... var last = thead[thead.length - 1]; last.parentNode.removeChild(last); The element will be removed from the DOM, as well as the thead list. – user1106925 Commented Jul 5, 2012 at 16:24

3 Answers 3

getElementsByTagName (docs) does not return an Array, it returns a NodeList. As said by the linked NodeList docs:

NodeList are used very much like arrays and it would be tempting to use Array.prototype methods on them. This is, however, impossible.

There are some Array like things you can do with a NodeList, and you can even .apply some Array.prototype methods to them, but you should read the docs to avoid the "gotchas", especially where problems with the NodeList being "live" could bite you.

getElementsByTagName() returns a DOM 2 NodeList, not an Array.

Technically, document.getElementsByTagName returns a NodeList object, which has no pop function.

Try alert(Array.isArray(thead)), and you'll see that it returns false