js实现图片点击弹出放大效果

点击图片，显示蒙板，放大图片的简单案例

HTML代码：

<div>
        <img height="100" width="100" src="https://img-blog.csdn.net/20180518162114673?watermark/2/text/aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3l1bnNpd2w1/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70" class="pic"/>
        <img height="100" width="100" src="https://img-blog.csdn.net/20180518162114673?watermark/2/text/aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3l1bnNpd2w1/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70" class="pic"/>
        <img height="100" width="100" src="https://img-blog.csdn.net/20180