CSS变量-交换值? [英] CSS Variables - Swapping values?

问题描述

我有一个非常简单的CSS变量问题.我想交换两个CSS变量，基本上是ES6中[a, b] = [b, a]的CSS等效项.这是一个简单的示例:

I have a very simple problem with CSS variables. I would like to swap two CSS variables, basically the CSS equivalent of [a, b] = [b, a] in ES6. Here's a simple example:

<p>White background</p>
<button>Black background</button>
<div>
  <p>Black background</p>
  <button>White background</button>
</div>

:root {
  --primary-color: #fff;
  --secondary-color: #000;
}

body {
  background-color: var(--primary-color);
}

button {
  background-color: var(--secondary-color);
}

div {
  /* i'd like to do the following: */
  --primary-color: var(--secondary-color);
  --secondary-color: var(--primary-color);

  /* so here, `--primary-color` would be `--secondary-color` from `:root`
   * and any children have these colors swapped as well
   */
  background-color: var(--primary-color);
}

但是，这失败了，因为CSS var()是实时绑定.我在这里想念什么吗?还是这是规范当前的工作方式?

However, this fails because CSS var()s are live bindings. Am I missing something here? Or is this the way the spec currently works?

推荐答案

您正在创建循环依赖项，因为您正在使用另一个属性来定义每个属性，因此这是行不通的.相反，您可以通过引入更多变量来尝试类似的操作:

You are creating a cyclic dependence because you are defining each property using the other one and this won't work. Instead you may try something like this by introducing more variables:

:root {
  --p:#fff;
  --s:#000;
  --primary-color: var(--p);
  --secondary-color: var(--s);
}

body {
  background-color: var(--primary-color);
}

button {
  background-color: var(--secondary-color);
}

div {
  /* i'd like to do the following: */
  --primary-color: var(--s);
  --secondary-color: var(--p);
  
  background-color: var(--primary-color);
}

<p>White background</p>
<button>Black background</button>
<div>
  <p>Black background</p>
  <button>White background</button>
</div>

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