实现点击按钮，数值累加的效果

<tr>
<td width="9%" align="right" nowrap>会员积分</td>
<td colspan="5" align="left">
<input type="text" name="jf" id="num" value="${map.POINT==null?'0':map.POINT}" disabled>
    
<input class="normal_btn" type="BUTTON" name="button1" value="积分履历" id="button1" onclick="selectScore('${ctx}/iclub/memberMng/MemberManageAction/getScore.do');" />

<input type="text" name="scope" id="numb" value="">  

<input class="normal_btn" type="button" name="button1"value="积分调整" onclick="btn()" />

<font color="red">*</font>输入正数，则添加积分；输入负数，则扣除积分。
</td>
</tr>

function btn() {
var num = document.getElementById("num");
var numb = document.getElementById("numb").value;
if (numb == "") {
numb = 0;
}
num.value = parseInt(num.value) + parseInt(numb);
}