弹窗查看内容时 内容滚动区域设置为body区

<button class="show-big-img" data-h="300">查看大图 h300</button>
<button class="show-big-img" data-h="3000">查看大图 h3000</button>


<div class="layer-shade"></div>
<div class="layer-wrap">
    <a href="javascript:;" class="layer-close">&times;</a>
    <div class="layer-content">
        <p class="show-origin-img">
            <a href="javascript:;">查看原图</a>
        </p>
        <div class="big-img">
            <div class="big-img__item">我是图片</div>
        </div>
    </div>
</div>

  1 body {
  2     &.layer-scroll-in-body {
  3         overflow: hidden;
  4     }
  5 }
  6 
  7 .layer-shade {
  8     display: none;
  9     position: fixed;
 10     width: 100%;
 11     height: 100%;
 12     top: 0;
 13     left: 0;
 14     background-color: #000;
 15     opacity: .15;
 16     
 17     &.visible {
 18         display: block;
 19     }
 20 }
 21 
 22 @keyframes bounceIn {
 23     to {
 24         opacity: 1;
 25         transform: scale(1);
 26     }
 27 }
 28 
 29 .layer-wrap {
 30     display: none;
 31     z-index: 1;
 32     position: fixed;    
 33     width: 70%;
 34     height: 50%;
 35     top: 100px;
 36     left: 100px;
 37     background-color: #000;
 38     border-radius: 3px;
 39     
 40     opacity: 0;
 41     transform: scale(.3);
 42     
 43     &.visible {
 44         display: block; 
 45         animation: bounceIn .5s;
 46         animation-fill-mode: both;
 47     }
 48     
 49     &.layer-scroll-in-body {
 50         position: absolute;
 51         height: auto;
 52     }
 53     
 54     &__wrapper {
 55         overflow: auto;
 56         position: fixed;
 57         top: 0;
 58         right: 0;
 59         width: 100%;
 60         height: 100%;
 61     }
 62 }
 63 
 64 .layer-close {
 65     position: absolute;
 66     top: -16px;
 67     right: -12px;
 68     width: 24px;
 69     height: 24px;
 70     text-decoration: none;
 71     color: #fff;
 72     background: #999;
 73     border-radius: 50%;
 74     border: 3px solid #fff;
 75     text-align: center;
 76     line-height: 22px;
 77     font-size: 22px;
 78     
 79     &:hover {
 80         background-color: #358eea;
 81     }
 82 }
 83 
 84 .layer-content {
 85     height: 100%;
 86     overflow: auto;
 87 }
 88 
 89 .show-origin-img {
 90     position: absolute;
 91     top: 5px;
 92     right: 20px;
 93     font-size: 12px;
 94     
 95     a {
 96         color: #fff;
 97         text-decoration: none;
 98         
 99         &:hover {
100             text-decoration: underline;
101         }
102     }
103     
104 }
105 
106 .big-img {
107     display: flex;
108     justify-content: center;
109     box-sizing: border-box;
110     padding: 20px;
111     
112     &__item {
113         display: flex;
114         justify-content: center;
115         align-items: center;
116         max-width: 100%;
117         width: 300px;
118         height: 3000px;
119         background-color: #c7bdb3;
120     }
121 }

// 显示弹窗
function showLayer(onShow, onClose) {
    var $body = $('body'),
        $layerShade = $('.layer-shade'),
        $layerWrap = $('.layer-wrap');
    
    // 查看大图
    $('.show-big-img').click(function() {
        $layerWrap.find('.big-img__item').css('height', $(this).attr('data-h'));
        
        // 显示前处理
        if (onShow && typeof onShow === 'function') {
            onShow($body, $layerWrap);
        }
       
        $layerShade.addClass('visible');
        $layerWrap.addClass('visible');
    });

    $('.layer-close').click(function() {
        // 关闭前处理
        if (onClose && typeof onClose === 'function') {
            onClose($body, $layerWrap);
        }
        
        $layerShade.removeClass('visible');    
        $layerWrap.removeClass('visible');
    });
}

// 显示弹窗，并设置弹窗内容滚动区为body区
function showLayerScrollInBody(setPageScroll) {
    // 模拟：确保显示弹窗前页面由垂直方向滚动条
    setPageScroll && $('.show-big-img').css('margin-bottom', 2000);
    
    showLayer(function($body, $layer) {
        // body设置 overflow: hidden
        $body.addClass('layer-scroll-in-body');
        
        $layer
            .addClass('layer-scroll-in-body')
            // 弹出层增加一层父级
            .wrap('<div class="layer-wrap__wrapper">');
    }, function($body, $layer) {
        // 关闭弹窗，则恢复
        $body.removeClass('layer-scroll-in-body');
        
        $layer
            .removeClass('layer-scroll-in-body')
            .unwrap();
    });
}


showLayer();

/* showLayerScrollInBody(); */

/* showLayerScrollInBody(true); */

$layer.wrap('<div class="layer-wrap__wrapper">');

&__wrapper {
        overflow: auto;
        position: fixed;
        top: 0;
        right: 0;
        width: 100%;
        height: 100%;
    }

$layer.addClass('layer-scroll-in-body')

&.layer-scroll-in-body {
        position: absolute;
        height: auto;
    }

$body.addClass('layer-scroll-in-body');

body {
    &.layer-scroll-in-body {
        overflow: hidden;
    }
}