Not much to say, please look at the example code
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title></title>
<script type="text/javascript">
function validation() {
var val = document.getElementById("txtNumber").value;
var regu = /^[1-9]\d*$/;
//var regu = /^([1-9][0-9]*){1,3}$/; 亲测可用
//var regu = /^\+?[1-9][0-9]*$/; 亲测可用
if (val != "") {
if (!regu.test(val)) {
document.getElementById("labResult").style.color = "red";
document.getElementById("labResult").innerHTML = "验证失败！";
} else {
document.getElementById("labResult").style.color = "green";
document.getElementById("labResult").innerHTML = "验证成功！";
}
}
}
</script>
</head>
<body>
<input id="txtNumber" name="txtNumber" type="text" />
<input id="btnValidation" name="btnValidation" type="button" value="校验" onclick="validation()" />
验证结果：<label id="labResult" ></label>
</body>
</html>
![[Web front-end] Node.js quick start](https://img.php.cn/upload/course/000/000/067/662b5d34ba7c0227.png)
