Change height value from px to % in .dotdotdot script

How can I change the height value from 100 pixels to a percentage value? Lets say 50%. I'm fairly new to javascript...

<script language="javascript" type="text/javascript">
$(document).ready(function(){
    $(".item-info-overlay p").dotdotdot({
        ellipsis:"...",
        wrap:"word",
        height: 100,
        after:"a.readmore",})
    });
</script>