Changing options position pitfall

gistfile1.js

/* 
 * // the following example failed to keep the last index.
 * 
 * temp = selElem.options[0];
 * selElem.options[0] = selElem.options[1];
 * selElem.options[1] = temp
 * return;
 */
var dash = selElem.options[0];
var all  = selElem.options[1];
selElem.options[0] = new Option(all.value, all.innerHTML);
selElem.options[1] = new Option(dash.value, dash.innerHTML);