给你个例子参考一下：
<html><head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
<meta name="GENERATOR" content="Microsoft FrontPage 4.0">
<meta name="ProgId" content="FrontPage.Editor.Document">
<title>New Page 1</title>
</head><body>
<input type="text" name="number" value="20" size="8" onblur="if(this.value.match(/\d+/)!=this.value && this.value!='' || parseInt(this.value)==0){alert('必须填入正整数数字！');this.select();this.focus();}"
</body></html>
<html><head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
<meta name="GENERATOR" content="Microsoft FrontPage 4.0">
<meta name="ProgId" content="FrontPage.Editor.Document">
<title>New Page 1</title>
</head><body>
<input type="text" name="number" value="20" size="8" onblur="if(this.value.match(/\d+/)!=this.value && this.value!='' || parseInt(this.value)==0){alert('必须填入正整数数字！');this.select();this.focus();}"
</body></html>
{
var stringCheck = /^(\d+)$/;
if(stringCheck.test(checkstring))
{
checkstring.match(stringCheck);
if(RegExp.$1>0) return true;
}
return false;
}