Q910 How can I pass selections back and forth between two multiple select options?

<script language="JavaScript"><!--
function deleteOption(object,index) {
    object.options[index] = null;
}

function addOption(object,text,value) {
    var defaultSelected = true;
    var selected = true;
    var optionName = new Option(text, value, defaultSelected, selected)
    object.options[object.length] = optionName;
}

function copySelected(fromObject,toObject) {
    for (var i=0, l=fromObject.options.length;i<l;i++) {
        if (fromObject.options[i].selected)
            addOption(toObject,fromObject.options[i].text,fromObject.options[i].value);
    }
    for (var i=fromObject.options.length-1;i>-1;i--) {
        if (fromObject.options[i].selected)
            deleteOption(fromObject,i);
    }
}

function copyAll(fromObject,toObject) {
    for (var i=0, l=fromObject.options.length;i<l;i++) {
        addOption(toObject,fromObject.options[i].text,fromObject.options[i].value);
    }
    for (var i=fromObject.options.length-1;i>-1;i--) {
        deleteOption(fromObject,i);
    }
}
//--></script>

<form>

<table><tr><td>

<select name="select1" multiple size="7">
<option>zero
<option>one
<option>two
<option>three
<option>four
<option>five
<option>six
</select>

</td><td>

<input type="button" value=" > " onClick="if (document.images) copySelected(this.form.select1,this.form.select2)">
<p>
<input type="button" value=" < " onClick="if (document.images) copySelected(this.form.select2,this.form.select1)">
<p>
<input type="button" value=">>" onClick="if (document.images) copyAll(this.form.select1,this.form.select2)">
<p>
<input type="button" value="<<" onClick="if (document.images) copyAll(this.form.select2,this.form.select1)">

</td><td>

<select name="select2" multiple size="7">
</select>

</td></tr></table>

</form>