SOURCE

// 获取弹窗
var modal = document.getElementById('myModal');
 
// 获取图片插入到弹窗 - 使用 "alt" 属性作为文本部分的内容
var img = document.getElementById('myImg');
var modalImg = document.getElementById("img01");
var captionText = document.getElementById("caption");
img.onclick = function(){
    modal.style.display = "block";
    modalImg.src = this.src;
    captionText.innerHTML = this.alt;
}
 
// 获取 <span> 元素，设置关闭按钮
var span = document.getElementsByClassName("close")[0];
 
// 当点击 (x), 关闭弹窗
span.onclick = function() { 
  modal.style.display = "none";
}

<!-- 触发弹窗 - 图片改为你的图片地址 -->
<img id="myImg" src="https://ss1.bdstatic.com/70cFvXSh_Q1YnxGkpoWK1HF6hhy/it/u=2213111953,2032525380&fm=23&gp=0.jpg" alt="念桥边红药" width="300" height="200">
 
<!-- 弹窗 -->
<div id="myModal" class="modal">
 
  <!-- 关闭按钮 -->
  <span class="close" onclick="document.getElementById('myModal').style.display='none'">&times;</span>
 
  <!-- 弹窗内容 -->
  <img class="modal-content" id="img01">
 
  <!-- 文本描述 -->
  <div id="caption"></div>
</div>

/* 触发弹窗图片的样式 */
#myImg {
    border-radius: 5px;
    cursor: pointer;
    transition: 0.3s;
}
 
#myImg:hover {opacity: 0.7;}
 
/* 弹窗背景 */
.modal {
    display: none; /* Hidden by default */
    position: fixed; /* Stay in place */
    z-index: 1; /* Sit on top */
    padding-top: 100px; /* Location of the box */
    left: 0;
    top: 0;
    width: 100%; /* Full width */
    height: 100%; /* Full height */
    overflow: auto; /* Enable scroll if needed */
    background-color: rgb(0,0,0); /* Fallback color */
    background-color: rgba(0,0,0,0.9); /* Black w/ opacity */
}
 
/* 图片 */
.modal-content {
    margin: auto;
    display: block;
    width: 80%;
    max-width: 700px;
}
 
/* 文本内容 */
#caption {
    margin: auto;
    display: block;
    width: 80%;
    max-width: 700px;
    text-align: center;
    color: #ccc;
    padding: 10px 0;
    height: 150px;
}
 
/* 添加动画 */
.modal-content, #caption { 
    -webkit-animation-name: zoom;
    -webkit-animation-duration: 0.6s;
    animation-name: zoom;
    animation-duration: 0.6s;
}
 
@-webkit-keyframes zoom {
    from {-webkit-transform:scale(0)} 
    to {-webkit-transform:scale(1)}
}
 
@keyframes zoom {
    from {transform:scale(0)} 
    to {transform:scale(1)}
}
 
/* 关闭按钮 */
.close {
    position: absolute;
    top: 15px;
    right: 35px;
    color: #f1f1f1;
    font-size: 40px;
    font-weight: bold;
    transition: 0.3s;
}
 
.close:hover,
.close:focus {
    color: #bbb;
    text-decoration: none;
    cursor: pointer;
}
 
/* 小屏幕中图片宽度为 100% */
@media only screen and (max-width: 700px){
    .modal-content {
        width: 100%;
    }
}