选择CSS中的前一个兄弟 - 更新时间轴[复制]

Question

这个问题在这里已有答案：

• Is there a “previous sibling” selector? 15个答案

我正在寻找一个CSS解决方案，将背景颜色应用于当前事件上一个事件的垂直时间轴

.timeline {
    position: relative;
    display: flex;
    margin: 10px;
    flex-direction: column;
}

.timeline .event {
    position: relative;
    display: flex;
    flex-direction: row;
    padding-left: 15px;
}

.timeline .event::before {
    content: '';
    position: absolute;
    top: 0px;
    left: 2px;
    bottom: 0px;
    width: 2px;
    background: #d9d9d9;
}

.timeline.descending .event.open + .event:nth-child(3n-1)::before {
    background: #555555;
} 

<div class="timeline descending">
    <div class="event">
        Event 1
    </div>
    <div class="event">
        Event 2
    </div>
    <div class="event open">
        Event 3
    </div>
    <div class="event">
        Event 4
    </div>
    <div class="event">
        Event 5
    </div>
    <div class="event">
        Event 6
    </div>
</div>

在上面的例子中，我为Event 3打开了类，我试图用Event 2改变#555555轴的颜色，我写的代码像 -

.timeline.descending .event.open + .event:nth-child(3n-1)::before {
    background: #555555;
}

哪个没用！

但是，当我修改代码时

.timeline.descending .event + .event:nth-child(3n-1)::before {
    background: #555555;
}

.timeline {
    position: relative;
    display: flex;
    margin: 10px;
    flex-direction: column;
}

.timeline .event {
    position: relative;
    display: flex;
    flex-direction: row;
    padding-left: 15px;
}

.timeline .event::before {
    content: '';
    position: absolute;
    top: 0px;
    left: 2px;
    bottom: 0px;
    width: 2px;
    background: #d9d9d9;
}

/* .timeline .event:nth-child(1)::before {
    background: #000000;
} */

.timeline.descending .event + .event:nth-child(3n-1)::before {
    background: #555555;
}

<div class="timeline descending">
    <div class="event">
        Event 1
    </div>
    <div class="event">
        Event 2
    </div>
    <div class="event open">
        Event 3
    </div>
    <div class="event">
        Event 4
    </div>
    <div class="event">
        Event 5
    </div>
    <div class="event">
        Event 6
    </div>
</div>

我能够运行它，它给了我部分结果。我对nth-child和nth-last-child工作的理解有限，任何帮助都会受到赞赏。

Answer 1

我不确定您是否可以选择以前的元素，但是如果您将问题翻到头上，则可以选择以下元素。

例如：

.timeline {
    position: relative;
    display: flex;
    margin: 10px;
    flex-direction: column;
}

.timeline .event {
    position: relative;
    display: flex;
    flex-direction: row;
    padding-left: 15px;
}

.timeline .event::before {
    content: '';
    position: absolute;
    top: 0px;
    left: 2px;
    bottom: 0px;
    width: 2px;
    background: #555;
}

.timeline.descending .event.open ~ .event::before {
    background: #d9d9d9;
}

<div class="timeline descending">
    <div class="event">
        Event 1
    </div>
    <div class="event">
        Event 2
    </div>
    <div class="event open">
        Event 3
    </div>
    <div class="event">
        Event 4
    </div>
    <div class="event">
        Event 5
    </div>
    <div class="event">
        Event 6
    </div>
</div>

Answer 2

如果您只想更改(n)th索引（您可以逐步更改n，您可以从第二个索引开始选择;对于第一个兄弟，您可以使用.timeline.descending .event:first-child::before）：

.timeline.descending .event:nth-child(1) + .event::before {
    background: #555555;
}

在这个例子中你也可以用:nth-child(1)交换:first-child。

请注意，CSS中有no previous sibling selector。

.timeline {
    position: relative;
    display: flex;
    margin: 10px;
    flex-direction: column;
}

.timeline .event {
    position: relative;
    display: flex;
    flex-direction: row;
    padding-left: 15px;
}

.timeline .event::before {
    content: '';
    position: absolute;
    top: 0px;
    left: 2px;
    bottom: 0px;
    width: 2px;
    background: #d9d9d9;
}


.timeline.descending .event:nth-child(1) + .event::before {
    background: #555555;
}

<div class="timeline descending">
    <div class="event">
        Event 1
    </div>
    <div class="event">
        Event 2
    </div>
    <div class="event open">
        Event 3
    </div>
    <div class="event">
        Event 4
    </div>
    <div class="event">
        Event 5
    </div>
    <div class="event">
        Event 6
    </div>
</div>

或者，如果你使用JavaScript很好，你可以使用：

const evt = document.querySelectorAll('.event');
for(let i = 0; i < evt.length ; i++) {
    if(((i+1) != evt.length) && evt[i+1].classList.contains('open')){
      var styleElem = document.head.appendChild(document.createElement("style"));   
      styleElem.innerHTML = ".timeline.descending .event:nth-child("+ (i+1) + ")::before {background: #555555;}";
    }
}

const evt = document.querySelectorAll('.event');
for(let i = 0; i < evt.length ; i++) {
    if(((i+1) != evt.length) && evt[i+1].classList.contains('open')){
      var styleElem = document.head.appendChild(document.createElement("style"));
      styleElem.innerHTML = ".timeline.descending .event:nth-child("+ (i+1) + ")::before {background: #555555;}";
    }
}

.timeline {
    position: relative;
    display: flex;
    margin: 10px;
    flex-direction: column;
}

.timeline .event {
    position: relative;
    display: flex;
    flex-direction: row;
    padding-left: 15px;
}

.timeline .event::before {
    content: '';
    position: absolute;
    top: 0px;
    left: 2px;
    bottom: 0px;
    width: 2px;
    background: #d9d9d9;
}

<div class="timeline descending">
    <div class="event">
        Event 1
    </div>
    <div class="event">
        Event 2
    </div>
    <div class="event open">
        Event 3
    </div>
    <div class="event">
        Event 4
    </div>
    <div class="event">
        Event 5
    </div>
    <div class="event">
        Event 6
    </div>
</div>