Fastest way to select all elements in a *ListBox*

[A]

I am trying to select all the elements in a Listbox/SelectBox. At the moment I am using the following function *which is working*, the only thing is it takes around 10 seconds to select all elements(of which there are 652). I'm a beginner at javascript so I was wondering whether anyone knew of a faster way to select all elements.

//selectBox is the selectbox ID, selectall is a boolean whether to select all elements,
//ensureOneSelected applies when false is specified for selectall
//it then ensures that the first element is always selected.

function selectAll(selectBox, selectAll, ensureOneSelected) {
// have we been passed an ID
var selectBoxElement = null;
var selectBoxOption = null;

var boolSelect = selectAll;

if (typeof selectBox == "string") {
    selectBoxElement = document.getElementById(selectBox);
    selectBoxOption = selectBoxElement.options;
}
// is the select box a multiple select box?
if (selectBoxElement.type == "select-multiple") {
    var max = (selectBoxOption.length);

    var modMaxUnrollFactor = (max % 4);

    max -= modMaxUnrollFactor ;

    for(var i = 0; i < max; i+=4){
        selectBoxOption\[i\].selected = boolSelect;
        selectBoxOption\[i + 1\].selected = boolSelect;
        selectBoxOption\[i + 2\].selected = boolSelect;
        selectBoxOption\[i + 3\].selected = boolSelect;

    }
    for (var i = max; i < selectBoxOption.length; i++) {
        selectBoxOption\[i\].selected = boolSelect;
    }

    if (typeof ensureOneSelected == "boolean") {
        if(selectBoxOption\[0\].selected == false)
        {
            selectBoxOption\[0\].selected = ensureOneSelected;
        }
    }
}

}

thanks in advance

My blog:[^]

[BobJanova]

What is with the unroll factor and two loops? That is pointless ... running a for loop 600 times isn't what's slow. Manipulating the DOM can be slow. You might do better to get .innerHTML, do a regex replace for '<option( selected)?' with either '<option' or '<option selected', and then reassign .innerHTML.

[A]

BobJanova wrote:

Manipulating the DOM can be slow. You might do better to get .innerHTML, do a regex replace for '<option( selected)?' with either '<option' or '<option selected', and then reassign .innerHTML.

Thanks, I'll look into it.

BobJanova wrote:

What is with the unroll factor and two loops? That is pointless ... running a for loop 600 times isn't what's slow.

I'm a c/c++ programmer predominately, force of habit :)

My blog:[^]

[A]

Developed a working solution on IE8 though I did run into a select option truncate bug where the first option in innerHTML is removed. :| But in the end I developed a workaround for this bug and have a working hack solution which is much much faster, so all is good. :) cheers.:thumbsup:

My blog:[^]