js 透明层蒙层弹窗

设置弹出的div样式为

    display: block;
    background: beige;
    position: absolute;
    top: 30%;
    left: 30%;
    width: 27%;

设置一个before 样式

    position: fixed;
    top: 0;
    left: 0;
    z-index: 800;
    width: 100%;
    height: 100%;
    background: rgba(0,0,0,0.5);
    content: '';
    opacity: 0;
    -webkit-transition: opacity 0.5s;
    transition: opacity 0.5s;
    pointer-events: none;

弹出后修改before 样式 修改透明度 opacity: 1.8;

设置 z-index