<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>菜鸟教程(runoob.com)</title>
</head>
<body>

<p>搜索字符串 "runoob", 并显示匹配的起始位置：</p>
<button onclick="myFunction()">点我</button>
<p id="demo"></p>
<script>
function myFunction() {
    var str = "Visit Runoob!"; 
    var n = str.search(/Runoob/i);
    document.getElementById("demo").innerHTML = n;
}
</script>

</body>
</html>

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>菜鸟教程(runoob.com)</title>
</head>
<body>

<p>搜索字符串 "Runoob", 并显示匹配的起始位置：</p>
<button onclick="myFunction()">点我</button>
<p id="demo"></p>
<script>
function myFunction() {
    var str = "Visit Runoob!"; 
    var n = str.search("Runoob");
    document.getElementById("demo").innerHTML = n;
}
</script>

</body>
</html>

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>菜鸟教程(runoob.com)</title>
</head>
<body>

<p>替换 "microsoft" 为 "Runoob" :</p>
<button onclick="myFunction()">点我</button>
<p id="demo">Visit Microsoft!</p>
<script>
function myFunction() {
    var str = document.getElementById("demo").innerHTML; 
    var txt = str.replace(/microsoft/i,"Runoob");
    document.getElementById("demo").innerHTML = txt;
}
</script>

</body>
</html>

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>菜鸟教程(runoob.com)</title>
</head>
<body>

<p>替换 "Microsoft" 为 "Runoob" :</p>
<button onclick="myFunction()">点我</button>
<p id="demo">请访问 Microsoft!</p>
<script>
function myFunction() {
    var str = document.getElementById("demo").innerHTML; 
    var txt = str.replace("Microsoft","Runoob");
    document.getElementById("demo").innerHTML = txt;
}
</script>

</body>
</html>

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>菜鸟教程(runoob.com)</title>
</head>
<body>

<script>
var patt1=new RegExp("e");
document.write(patt1.test("The best things in life are free"));
</script>

</body>
</html>

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>菜鸟教程(runoob.com)</title>
</head>
<body>

<script>
var patt1=new RegExp("e");
document.write(patt1.exec("The best things in life are free"));
</script>

</body>
</html>

function isValid(str) { return /^\w+$/.test(str); }
str = "1234abd__"
document.write(isValid(str));
document.write("<br>");

str2 = "$32343#"
document.write(isValid(str2));
document.write("<br>");
val = "123456"
var isletter = /^[a-zA-Z]+$/.test(val);
document.write(isletter);
document.write("<br>");

val2 = "asaaa"
var isletter2 = /^[a-zA-Z]+$/.test(val2);
document.write(isletter2);
val = "123456"
var isnum = /^\d+$/.test(val);
document.write(isnum);
document.write("<br>");

val2 = "as123"
var isnum2 = /^\d+$/.test(val2);
document.write(isnum2);

 

/*是否带有小数*/
function    isDecimal(strValue )  {  
   var  objRegExp= /^\d+\.\d+$/;
   return  objRegExp.test(strValue);  
}  

/*校验是否中文名称组成 */
function ischina(str) {
    var reg=/^[\u4E00-\u9FA5]{2,4}$/;   /*定义验证表达式*/
    return reg.test(str);     /*进行验证*/
}

/*校验是否全由8位数字组成 */
function isStudentNo(str) {
    var reg=/^[0-9]{8}$/;   /*定义验证表达式*/
    return reg.test(str);     /*进行验证*/
}

/*校验电话码格式 */
function isTelCode(str) {
    var reg= /^((0\d{2,3}-\d{7,8})|(1[3584]\d{9}))$/;
    return reg.test(str);
}

/*校验邮件地址是否合法 */
function IsEmail(str) {
    var reg=/^\w+@[a-zA-Z0-9]{2,10}(?:\.[a-z]{2,4}){1,3}$/;
    return reg.test(str);
}


function  fun1(){
    if(!isStudentNo(document.getElementById("sno").value)){
        alert("学生编号是8位数字");
        document.getElementById("sno").focus();
        return false;
    }

    if(!ischina(document.getElementById("username").value)){
        alert("学生姓名必须填写中文");
        document.getElementById("username").focus();
        return false;  
    }

    if(!IsEmail(document.getElementById("email").value)){
        alert("邮箱地址错误");
        document.getElementById("email").focus();
        return false;  
    }

    if(!isTelCode(document.getElementById("tel").value)){
        alert("电话号码不对");
        document.getElementById("tel").focus();
        return false;  
    }

    /*运行到这里说明验证通过返回true    submit提交按钮起作用提交表单*/
    alert("提交成功")
    return false;   // 这边设置禁止提交，实际项目需要改为 true
}
<form name="myform" action="" onsubmit="return fun1()">
<div align="center">
<table border="1" width="60%" >
    <tr>
        <td colspan=2 align=center><h3>学生信息管理</h3></td>
    </tr>
    <tr>
        <td height="39" width="463" bgcolor="#006699">
        <font color="#FFFF00">学生编号：</font><input type="text" maxlength=10 id="sno" value="12345678">(8位数字)
        </td>

        <td height="39" width="463" bgcolor="#006699">
        <font color="#FFFF00">学生名字：</font><input type="text" maxlength=10 id="username" value="刘训">(中文)
        </td>
    </tr>
    <tr>
        <td height="39" width="463" bgcolor="#006699">
        <font color="#FFFF00">邮箱地址：</font><input type="text" maxlength=10 id="email" value="1056125478@qq.com">
        </td>
        
       <td height="39" width="463" bgcolor="#006699">
        <font color="#FFFF00">电话号码：</font><input type="text" maxlength=11 id="tel" value="15574074751">
        </td>
    </tr>
    <tr>
        <td  height="53" width="985" bgcolor="#006699" colspan="2" align=center>
        <input type="submit" value="使用submit按钮提交表单">
        </td>
    </tr>
</table>