Javascript optimisation - while.js

/* 
Using as a benchmark the task of iterating over a live collection produced by getElementsByTagName. IE/Win, Gecko and Safari all agree as to the fastest means - use a while loop and store the live collection in a variable:
*/

var i = 0, el, els = document.getElementsByTagName(nodeName);
while (el = els[i++]) {
    // [...]
}