CSS伪类:empty和:only-child

<div class="cs-module"></div>

.cs-module:empty {
    display: none;
}

<dl>
    <dt>姓名：</dt>
    <dd>张三</dd>
    <dt>性别：</dt>
    <dd></dd>
    <dt>手机：</dt>
    <dd></dd>
    <dt>邮箱：</dt>
    <dd></dd>
</dl>
dd:empty::before {
    content: ‘暂无‘;
    color: gray;
}

td:empty::before{
    content: ‘-‘;
    color: gray;
}

.cs-search-module:empty::before{
    content: ‘没有搜索结果‘；
    display: block;
    line-height: 300px;
    text-align: center;
    color: gray;
}

.cs-article-module:empty::before{
    content: ‘暂无数据；
    display: block;
    line-height: 300px;
    text-align: center;
    color: gray;
}

<!-- 1. 只有加载图片 -->
<div class="cs-loading">
    <img src="./loading.png" class="cs-loading-img">
</div>
<!-- 2. 只有加载文字 -->
<div class="cs-loading">
    <p class="cs-loading-p">正在加载中...</p>
</div>
<!-- 3. 加载图片和加载文字同时存在 -->
<div class="cs-loading">
    <img src="./loading.png" class="cs-loading-img">
    <p class="cs-loading-p">正在加载中...</p>
</div>

.cs-loading {
    height: 150px;
    position: relative;
    text-align: center;
    /* 与截图无关，截图示意用 */
    border: 1px dotted;
}
/* 图片和文字同时存在时在中间留点间距 */
.cs-loading-img {
    width: 32px; height: 32px;
    margin-top: 45px;
    vertical-align: bottom;
}
.cs-loading-p {
    margin: .5em 0 0;
    color: gray;
}
/* 只有图片的时候居中绝对定位 */
.cs-loading-img:only-child {
    position: absolute;
    left: 0; right: 0; top: 0; bottom: 0;
    margin: auto;
}
/* 只有文字的时候行号近似垂直居中 */
.cs-loading-p:only-child {
    margin: 0;
    line-height: 150px;
}