更改样式：before和：after伪元素？

问题描述：

这是我的代码看起来像：

This is what my code looks like:

$('.mainSpan:before').css('background','url(_gfx/cmn/main_bg.png)');

这似乎不工作，所以我问是否甚至可能添加

This does not seem to work so I'm asking if it's even possible to add background images to shadow elements with jQuery.

答

不能使用Javascript直接访问伪元素，因为它们不是部分的DOM。您可以使用可选的第二个参数（当前使用的大多数浏览器，但不是所有浏览器）来阅读它们的样式 - .getComputedStyle（） ，但您无法直接更改其样式。

It's not possible to directly access pseudo-elements with Javascript as they're not part of the DOM. You can read their style using the optional second argument - which most, although not all, browsers in current use support - in .getComputedStyle() but you can't directly change their style.

但是，您可以通过添加一个新的样式元素包含新规则。例如：

However, you could change their style indirectly by adding in a new style element containing new rules. For example:

http://jsfiddle.net/sjFML/

初始CSS分配具有绿色背景的：before 伪元素，通过插入一个新的样式元素，可以将其设置为黑色。

The initial CSS assigns the :before pseudo-element with a green background, which is turned to black by inserting a new style element.

HTML：

<div id="theDiv"></div>

CSS：

#theDiv {
    height: 100px;
    background: red;
}

#theDiv:before {
    content:' ';
    display: block;
    width: 50px;
    height: 50px;
    background: green;
}

Javascript：

Javascript:

var styleElem = document.head.appendChild(document.createElement("style"));

styleElem.innerHTML = "#theDiv:before {background: black;}";

更改样式：before和：after伪元素？

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