<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>demo</title>
</head>
<body>
    <span data-before='哈哈哈'>sdsd</span>
    <button onclick="change()">点击改变</button>
</body>
<style>
    span::before{
        content: attr(data-before);
    }
</style>
<script>
    let change = ()=>{
        let oSpan = document.querySelector("span");
        oSpan.setAttribute("data-before","改变")
    };
</script>
</html>

 

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