Javascript: Swapping select box options

Ah, but be careful

The important thing to remember about using this type of function is that you have to select all of the options in the select box before submitting for them to be sent to your server-side page. This type of script can pose accessibility problems as the normal behaviour of a select box is changed.

function swapSelectOptions(selectFrom,selectTo,swapAll) { 
    if (typeof(selectFrom) == "string") {
        availableitems = document.getElementById(selectFrom); 
    }
    if (typeof(selectTo) == "string") { 
        selecteditems= document.getElementById(selectTo); 
    } 
    for (var i = 0; i < availableitems.length; i++) { 
        if (availableitems.options[i].selected || swapAll) { 
            selecteditems.options[selecteditems.options.length] = new Option(availableitems.options[i].text);
            selecteditems.options[selecteditems.options.length-1].value = availableitems.options[i].value;
            availableitems.options[i].selected = false; availableitems.options[i] = null; i--;
        }
    }
}