struts通过javascript使按钮变灰为不可用，灰色按钮

struts页面用javascript来实现使按钮的变灰

<
html:form
 
action
=
"12.do"
 
method
=
"post"
>
<
html:button
 
property
=
"bb"
 
onclick
=
"test();"
>
退出
</
html:button
>
</
html:form
>

<
script
 
language
=
"javascript"
 
type
=
"text/javascript"
>
function test()
{
 document.forms[0]
.bb.disabled
   =   
true
   ;
}
</
script
>

<html:form action="12.do" method="post">
<html:button property="bb" onclick="test();">退出</html:button>
</html:form>

<script language="javascript" type="text/javascript">
function test()
{   
 document.forms[0].bb.disabled   =   true   ;   
}
</script>

 按下这个按钮，他自己就变成灰色且不可点的了