Mega Code Archive
Set select to multiple selected
<![CDATA[
<html>
<body>
Choose your Ice Creams<br>
<select name="mySelect" rows="10">
<option>A</option>
<option>B</option>
<option>C Chip</option>
<option>D</option>
</select>
<button onclick="mySelect.multiple=true;">Multiple</button>
<button onclick="mySelect.multiple=false;">Single</button>
</body>
</html>
]]>