修改元素：在React中以编程方式在CSS规则之前

Question

我有一个元素，其:before样式必须根据计算进行修改。

export class Content extends React.Component {
    render() {
        return (
            <div className="ring-base">
               <div className="ring-left" style={{/* Change here */}}></div>
               <div className="ring-right" style={{/* Change here */}}></div>
               <div className="ring-cover">
                   <div className="ring-text">10%</div>
               </div>
            </div>
        );
    }
}

CSS代码：

.ring-base {
    position: absolute;
    height: 200px;
    width: 200px;
    border-radius: 50%;
    background: red;
    transform: rotate(90deg);
    overflow:hidden;
}
.ring-cover {
    position: absolute;
    height: 180px;
    width: 180px;
    background: #fff;
    border-radius: 50%;
    top: 5%;
    left: 5%;
}

.ring-cover .ring-text {
    position: absolute;

    width: 100%;
    height: 100%;
    text-align: center;
    font-size: 2em;
    display: flex;
    justify-content:center;
    align-content:center;
    flex-direction:column;
    transform: rotate(-90deg);
}

.ring-right, .ring-left {
    height: 100px;
    width: 200px;
    overflow: hidden;
    position: absolute;  
}

.ring-right:before, .ring-left:before {
    height: inherit;
    width: inherit;
    position: absolute;
    content: "";
    border-radius: 100px 100px 0 0;
    background-color: grey;
    transform: rotate(0deg);
}

.ring-right {
    -webkit-transform-origin: 50% 0%;
    -moz-transform-origin: 50% 0%;
    -ms-transform-origin: 50% 0%;
    transform-origin: 50% 0%;
    transform: rotateZ(0deg);
}

.ring-left {
    transform: rotate(180deg);
    -webkit-transform-origin: 50% 100%;
    -moz-transform-origin: 50% 100%;
    -ms-transform-origin: 50% 100%;
    transform-origin: 50% 100%;
}

.ring-right:before {
    -webkit-transform-origin: 50% 100%;
    -moz-transform-origin: 50% 100%;
    -ms-transform-origin: 50% 100%;
    transform-origin: 50% 100%;
    transform: rotate(0deg);
}

.ring-left:before {
    -webkit-transform-origin: 50% 100%;
    -moz-transform-origin: 50% 100%;
    -ms-transform-origin: 50% 100%;
    transform-origin: 50% 100%;
    -webkit-transform: rotate(0deg);
    -moz-transform: rotate(0deg);
    -ms-transform: rotate(0deg);
    transform: rotate(0deg);

}

要求是能够通过ReactJS .ring-left:before和.ring-right:before通过ReactJS
更新transform属性。

如果有一种方法可以不更新:before类，也可以完全不使用CSS :before，则也建议这样做。

Answer 1

您可以重复document.styleSheets设置.style的.cssRules地方.selectorText比赛伪选择

let sheets = document.styleSheets;

let selector = "div::before";

let replacementContent = '"after"';

for (let sheet of sheets) {

  for (let rule of sheet.cssRules) {

    if (rule.selectorText === selector) {

      rule.style["content"] = replacementContent;

    }

  }

}


div:before {

  content: "before";

  color: red;

  font-weight: bold;

  text-align: center;

  text-shadow: 2px 2px 2px #000;

  background: green;

  width: 50px;

  height: 50px;

  display: block;

}


<div></div>