判断输入为数字,该怎么处理

判断输入为数字
<tr>
  <td> 部门： </td>
  <td   colspan= "3 ">
    <input   type= "checkbox "   name= "codepts <%=i+1%> "   value= " <%=TSysDept.getDeptid()%> ">
    <input   name= "copercent_ <%=TSysDept.getDeptid()   %> "   class= "in "   size= "5 "   value= " "   onpropertychange= "sumNum(this) ">
    <input   type= "hidden "   name= "porderd_ <%=TSysDept.getDeptid()   %> "   value= " <%=porderd   %> ">
  </td>
</tr>

怎样判断输入为数字
onpropertychange= "sumNum(this)   这个脚本应该怎么实现?


[解决办法]
function sumNum(obj)
{
var num=obj.value;
if(!num.match(/^[1-9](\d*)?(\.[\d]+)?$/))
{
event.keyCode=0;
event.returnValue=0;
}
}