获得多项选择列表框的选中选项

 <form>
        <select id="sel" size="20" multiple="multiple"> 
            <option value="1">01 </option> 
            <option value="2">02 </option> 
            <option value="3">03 </option> 
            <option value="4">04 </option> 
            <option value="5">05 </option> 
            <option value="6">06 </option> 
            <option value="7">07 </option> 
        </select> 
<input type="button" value="click" onclick="doit()" /> 
</form>
<script language="javascript" type="text/javascript"> 
function doit() 
{
    var sel = document.forms[0].sel;
    for(var i=0;i<sel.options.length;i++){
        if(sel.options[i].selected) alert(sel.options[i].value);
    }
} 

</script>