在javascript中如何用动态的选中一个list中的所有项?

[one_bird]

如题~

[liuzxit]

<select size="10" multiple id="s1">
<option>ass</option>
<option>sgdfhgdf</option>
<option>ass</option>
<option>sgdfhgdf</option>
</select>

<input type="button" value="selectAll" onclick="for(var i=0;i<s1.length;i++)s1.options[i].selected=true">

[anita2li]

<Script Language="JavaScript">
function selectAll()
{
for(var i=0;i<sel.length;i++)
sel.options(i).selected=true;
}
</Script>
<select id="sel" onclick="selectAll()" size="1" MULTIPLE >
<option value="1">1</option>
<option value="2">2</option>
<option value="3">3</option>
<option value="4">4</option>
</select>