判断填写字数的限制

程序代码：

<script language=javascript>

function gbcount(message,total,used,remain)

{

var max;

max&n, bsp;= total.value;

if(message.value.length > max){

message.value = message.value.substring(0,max);

used.value = max;

remain.value = 0;

alert('留言不能超过规定的字数!');

}

else{

used.value = message.value.length;

remain.value = max - used.value;

}

}

</script>

<form name='myform' >

<textarea name='GuestContent' cols='59' rows='6' onkeydown=gbcount(this.form.GuestContent,this.form.total,this.form.used,this.form.remain); onkeyup=gbcount(this.form.GuestContent,this.form.total,this.form.used,this.form.remain);></textarea>

最多字数：<INPUT disabled maxLength=4 name=total size=3 value=20>