<script>
function showMessage(msg){
alert(msg)
}
</script>
<form name="formName" >
<input type="button" value="showMessage" onclick="showMessage('<bean:write name="beanName" property="beanProperty" ignore="true">')">
</form>

<script>


</script>
<form name="formName" >
<input type="button" value="showMessage" onclick="showMessage()">
<input type="hidden" name="msg" value="<bean:write name="beanName" property="beanProperty" ignore="true">" />
</form>


function showMessage(){
var msg=document.formName.msg.value;
alert(msg)
}