判断输入信息为数值类型

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<HEAD>
<TITLE> New Document </TITLE>
<META NAME="Generator" CONTENT="EditPlus">
<META NAME="Author" CONTENT="">
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<script>
function isInt(s)
{
  if(s.value!="")
  {
   var p=/^[0-9]{1,20}$/;
   if (!p.exec(s.value))
   {
    alert("类型不对,必须填写数值类型!");
    s.value="";
    s.focus();
    return;
   }
  }
}
</script>
</HEAD>