Home >Web Front-end >JS Tutorial >Introduction to JavaScript regular expressions starting with a letter
Free learning recommendation: javascript video tutorial
Form Verification: Create a form and use JavaScript dom to add verification to the form.
Requirements:
<!DOCTYPE html><html lang="en"><!-- 表单校验:创建表单,使用JavaScript为表单添加校验.
1.验证用户名称,必须以字母开头,长度2-6位之间.
2.验证密码不能为空.
3.确认密码不能为空,要与密码一致. --><head>
<meta charset="UTF-8">
<title>Document</title>
<script type="text/javascript">
function checkForm() {
//获得用户名对象
var username = document.getElementById("username");
//---获得用户名输入框中的value值
var usernamevalue = username.value;
var Reg = /^[a-zA-Z][-_a-zA-Z0-9]{1,5}/;//JavaScript中的正则与Java的正则略有不同
if (usernamevalue.length >= 2 && usernamevalue.length <= 6 && Reg.test(usernamevalue)) {
//为span设置提示语
document.getElementById("usernameSpan").innerHTML = "<font color='green'> 用户名可用<font>";
} else {
document.getElementById("usernameSpan").innerHTML = "<font color='red'> 用户名必须以字母开头且长度在2-6之间<font>";
}
//获得密码value
var password = document.getElementById("password").value;
if (password == "") {
document.getElementById("passwordSpan").innerHTML = "<font color='red'>密码不能为空</font>";
} else {
document.getElementById("passwordSpan").innerHTML = "<font color='green'>密码可用</font>";
}
//获得确认密码
var repassword = document.getElementById("repassword").value;
if (repassword == password) {
document.getElementById("repasswordSpan").innerHTML = "<font color='green'>输入一致</font>";
} else {
document.getElementById("repasswordSpan").innerHTML = "<font color='red'>两次输入密码不一致</font>";
}
}
</script></head><body>
<h2>新用户注册</h2>
<p style="border: 1px solid sandybrown; width: 300px; height: 260px;">
<form action="">
<table cellspacing="15">
<tr>
<td>
用户名称:
</td>
<td>
<input type="text" id="username">
<span id="usernameSpan"></span>
</td>
</tr>
<tr>
<td>
密  码:
</td>
<td>
<input type="password" id="password">
<span id="passwordSpan"></span>
</td>
</tr>
<tr>
<td>
确认密码:
</td>
<td>
<input type="password" id="repassword">
<span id="repasswordSpan"></span>
</td>
</tr>
</table>
</form>
</p>
<input type="button" value="确认注册" onclick="checkForm()" /></body></html> Related free learning recommendations: javascript(Video)
The above is the detailed content of Introduction to JavaScript regular expressions starting with a letter. For more information, please follow other related articles on the PHP Chinese website!