js控制伪元素样式

//获取伪元素
// CSS代码
 #myId:before {
 content: "hello world!";
 display: block;
 width: 100px;
 height: 100px;
 background: red;
 }
 // HTML代码
 <div id="myId"></div>
 // JS代码
 var myIdElement = document.getElementById("myId");
 var beforeStyle = window.getComputedStyle(myIdElement, ":before");
 console.log(beforeStyle); // [CSSStyleDeclaration Object]
 console.log(beforeStyle.width); // 100px
 console.log(beforeStyle.getPropertyValue("width")); // 100px
 console.log(beforeStyle.content); // "hello world!

//更改样式:
 1 // CSS代码
 .red::before {
 content: "red";
 color: red;
 }
 .green::before {
 content: "green";
 color: green;
 }
 // HTML代码
 <div class="red">内容内容内容内容</div>
 // jQuery代码
 $(".red").removeClass('red').addClass('green');