That's easy... just look at EVERY element on the page and only do something if it's a checkbox.  Heck, there's only 5000+ elements, how long could that possibly take? 

for (iCount=0;iCount<=document.all.length;iCount++) {
    elm = document.all[iCount];
    if (elm.type == 'checkbox') {
        // snip
    }
}

chortlehoort:

Heck, there's only 5000+ elements, how long could that possibly take?

About half a millisecond 

Not at the youtube 0.1 thread.

To put it more clearly, the browser will iterate the 5000 elements many times over, doing CPU intensive stuff on each: load them, parse them, render them, resize them, ... One extra pass of 5000 string comparisons won't make noticeable difference.

That doesn't mean the code snippet isn't a WTF : using document.getElementsByTagName("input") instead of document.all (which is IE-script, not JavaScript) would be a good start to improve it

Using IDs for accessing dom elements via javascript is usually the route I go. If I remember correctly, getting a dom element by  document.getElementById('id') is  typically faster than  document.getElementsByTagName("input"),  and returns one object, instead of an array of them.  $0.02 deposited...

kaamoss:

Using IDs for accessing dom elements via javascript is usually the route I go.

True, but there are cases where you have no knowledge about the HTML, its elements and their id, if any, in particular when you make generic JS.

JvdL:

kaamoss:

Using IDs for accessing dom elements via javascript is usually the route I go.

True, but there are cases where you have no knowledge about the HTML, its elements and their id, if any, in particular when you make generic JS.

That's a good point, I guess I'm so used to not reusing that type of javascript code becase I can type it in emacs faster than I can think what I want it to do. For my code reuse, I try to pull out useful code into custom moo tool classes. Moo tools also gives a short_cut/cross browser way of accessing any dom element you want. I personally think that jQuery is better for this, but moo tools animations/ajax classes just seem to work better for me. If you're consistently writing js you're shooting yourself in the foot not leveraging some kind of js framework. 

This page has only 600+ elements. The average corp site -- that I build anyway -- has in the range of 100-200.

What kind of utterly insane page has five thousand elements?

(not including the Youtube 0.1 thread, which is accepted as being INSANE YAY)