使用原生JS实现一个带有遮盖层的模态框（HTML+CSS+JS）

使用原生JS实现一个带有遮盖层的简单的模态框（HTML+CSS+JS），废话不多说，代码如下（代码块内已做详细注释）：

HTML部分：

<!-- 触发按钮 -->
    <button id="triggerBtn">模态框</button>
    <!-- 模态框 -->
    <div id="myModal" class="modal">
        <div class="modal-content">
            <div class="modal-header">
                <h2>Basic Modal</h2>
                <span id="closeBtn" class="close">×</span>
            </div>
            <div class="modal-body">
              <hr>
                <p>Some contents...</p>
                <p>Some contents...</p>
                <p>Some contents...</p>
                <hr>
            </div>
            <div class="modal-footer">
                <button id="trueBtn" class="close">确定</button>
                <button id="falseBtn" class="close">取消</button>
            </div>
        </div>
    </div>

JS部分：

<script>  
    (function() {
        /*建立模态框对象*/
        var modalBox = {};
        /*获取模态框*/
        modalBox.modal = document.getElementById("myModal");
          /*获得trigger按钮*/
        modalBox.triggerBtn = document.getElementById("triggerBtn");
          /*获得关闭按钮*/
        modalBox.closeBtn = document.getElementById("closeBtn");
        modalBox.trueBtn = document.getElementById("trueBtn");
        modalBox.falseBtn = document.getElementById("falseBtn");
        /*模态框显示*/
        modalBox.show = function() {
            console.log(this.modal);
            this.modal.style.display = "block";
        }
        /*模态框关闭*/
        modalBox.close = function() {
            this.modal.style.display = "none";
        }
        modalBox.a = function(){
          this.modal.style.display = "none";
        }
        modalBox.b = function(){
          this.modal.style.display = "none";
        }
        /*当用户点击模态框内容之外的区域，模态框也会关闭*/
        modalBox.outsideClick = function() {
            var modal = this.modal;
            window.onclick = function(event) {
                    if(event.target == modal) {
                         modal.style.display = "none";
                    }
            }
        }
          /*模态框初始化*/
        modalBox.init = function() {
            var that = this;
            this.triggerBtn.onclick = function() {
                    that.show();
            }
            this.closeBtn.onclick = function() {
                that.close();
            }
            this.trueBtn.onclick=function(){
              that.a();
            }
            this.falseBtn.onclick=function(){
              that.b();
            }
            this.outsideClick();
        }
        modalBox.init();
    })();
</script>

CSS部分：

<style>  
      /*模态框*/
      .modal {
          display: none; /* 默认隐藏 */
          position: fixed; /* 根据浏览器定位 */
          z-index: 1; /* 放在顶部 */
          left: 0;
          top: 0;
          width: 100%; /* 全宽 */
          height: 100%; /* 全高 */
          overflow: auto; /* 允许滚动 */
          background-color: rgba(0,0,0,0.4); /* 背景色 */
      }
      /*模态框内容*/
      .modal-content {
          display: flex; /*采用flexbox布局*/
          flex-direction: column; /*垂直排列*/
          position: relative;
          background-color: #fefefe;
          margin: 15% auto; /*距顶部15% 水平居中*/
          padding: 20px;
          border: 1px solid #888;
          width: 30%;
          animation: topDown 0.4s; /*自定义动画，从模态框内容上到下出现*/
      }
      @keyframes topDown {
          from {top: -300px; opacity: 0}
          to {top: 0; opacity: 1}
      }
      /*模态框头部*/
      .modal-header {
          display: flex; /*采用flexbox布局*/
          flex-direction: row; /*水平布局*/
          align-items: center; /*内容垂直居中*/
          justify-content: space-between; 
      }
      /*关闭X 样式*/
      .close {
          color: #aaa;
          float: right;
          font-size: 28px;
          font-weight: bold;
      }
      .close:hover {
          color: black;
          text-decoration: none;
          cursor: pointer;
      }
 </style>