How to count the number of listbox using javascript

Question

I have an asp page in which the are number of listboxes.I want to count the number of listboxes using Javascript and also there is another requirement,i want to disable all the listboxes in that form

Answer 1

Using plain javascript:

document.getElementsByTagName('select').length

Using jQuery:

$('select').length

Answer 2

Using Protoype, you can do this:

$$('select').length