模态框案例

效果演示：

html+js代码如下：

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>模态框</title>
    <link rel="stylesheet" href="css/modal-box.css" />
  </head>
  <body>
    <!-- 页面头部 -->
    <header>
      <h2 class="title">php中文网-程序员开始的地方！</h2>
      <button onclick="showModal()">登录</button>
    </header>
    <!-- 模态框 -->
    <div class="modal">
      <!-- 1. 半透明的遮罩 -->
      <div class="modal-bg" onclick="closeModal()"></div>
      <!-- 2. 弹层表单 -->
      <form action="" class="modal-form">
        <fieldset style="display: grid; gap: 1em">
          <legend>会员登陆</legend>
          <input type="email" name="email" placeholder="请输入手机或邮箱账号" />
          <input type="password" name="password" placeholder="请输入密码" />
          <button>登录</button>
        </fieldset>
      </form>
    </div>
  </body>
</html>
<script>
  //js代码开始
  function showModal() {
    // 获取模态框元素
    const modal = document.querySelector(".modal");
    // 显示模态框
    modal.style.display = "block";
    // 焦点自动置入第一个输入框email
    modal.querySelector("input:first-of-type").focus();
  }
  function closeModal() {
    // 获取模态框元素
    const modal = document.querySelector(".modal");
    // 关闭模态框
    modal.style.display = "none";
  }
  //js代码结束
</script>

css代码：

/* 初始化 */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}
/* 头部 */
header {
    background-color: lightseagreen;
    padding: 0.5em 1em;
    display: flex;
}
/* logo  */
header .title {
    font-weight: lighter;
    font-style: italic;
    color: white;
    letter-spacing: 2px;
    text-shadow: 1px 1px 1px #555;
}
/* 登录按钮 */
header button {
    margin-left: auto;
    width: 5em;
    border: none;
    border-radius: 0.5em;
}
header button:hover {
    cursor: pointer;
    background-color: coral;
    color: #fff;
    box-shadow: 0 0 5px #fff;
    transition: 0.3s;
}
/* 模态框 */
.modal .modal-form fieldset {
    height: 15.5em;
    background-color: lightcyan;
    border: none;
    padding: 2em 3em;
    box-shadow: 0 0 5px #888;
}
/* 模态框表单标题 */
.modal .modal-form fieldset legend {
    padding: 7px 1.5em;
    background-color: lightseagreen;
    color: white;
}
.modal .modal-form fieldset input {
    height: 3em;
    padding-left: 1em;
    outline: none;
    border: 1px solid #ddd;
    font-size: 14px;
}
/* :focus: 表单控件,获取焦点时的样式 */
.modal .modal-form fieldset input:focus {
    box-shadow: 0 0 8px #888;
    border: none;
}
.modal .modal-form fieldset button {
    background-color: lightseagreen;
    color: white;
    border: none;
    height: 3em;
    font-size: 16px;
    height: 2.5em;
}
.modal .modal-form fieldset button:hover {
    background-color: coral;
    cursor: pointer;
}
/* 定位 */
.modal .modal-form {
    position: fixed;
    top: 10em;
    left: 38em;
    right: 38em;
}
/* 遮罩 */
.modal .modal-bg {
    position: fixed;
    /* 坐标全部清0,请定位到四个顶点 */
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background-color: rgb(0, 0, 0, 0.5);
}
.modal {
    display: none;
}