搞一个初始用例
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>BootStrap</title>
<style>
#result {
display: none;
}
</style>
</head>
<body>
<h2 class="title">注册</h2>
<form action="" id="myForm">
<div>
<label>姓名</label>
<input type="text" name="name">
</div>
<div>
<label>密码</label>
<input type="text" name="password">
</div>
<div>
<label>电话</label>
<input type="text" name="cellphone">
</div>
<div>
<label>地址</label>
<input type="text" name="address">
</div>
<div id="result">
</div>
<div class="operate">
<input type="submit">
</div>
</form>
<script>
var form = document.querySelector('#myForm');
var result = document.querySelector('#result');
form.addEventListener('submit', function(e) {
if (!document.querySelector('[name=password]').value) {
result.style.display = 'block'; // 块级显示
result.innerHTML = "密码为空";
e.preventDefault(); // 阻止表单的提交。
} else {
result.style.display = 'none';
}
})
</script>
</body>
</html>使用bootstrap
head中添加bootstrap的引用<link rel="stylesheet" href="https://cdn.bootcss.com/bootstrap/4.0.0/css/bootstrap.min.css" integrity="sha384-Gn5384xqQ1aoWXA+058RXPxPg6fy4IWvTNh0E263XmFcJlSAwiGgFAW/dAiS6JXm" crossorigin="anonymous">
原文：https://www.cnblogs.com/xxxuwentao/p/10157206.html