1、使用原生JS

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script>
        function switchUser() {
            let usernameEl = document.getElementById("username");
            const beforeVal = usernameEl.getAttribute("readonly");
            console.log("切换前状态：" + getStatus(beforeVal));
            if (beforeVal === null) {
                usernameEl.setAttribute("readonly", "readonly");
            } else {
                usernameEl.removeAttribute("readonly");
            }
            const afterVal = usernameEl.getAttribute("readonly");
            console.log("切换后状态：" + getStatus(afterVal));
        }

        function getStatus(readonlyVal) {
            if (readonlyVal === null) {
                return "读写"
            } else {
                return "只读"
            }
        }
    </script>
</head>
<body>

用户名：<input type="text" id="username" name="username"><br>
<button onclick="switchUser()">切换用户名readonly属性</button>

</body>
</html>

2、使用jquery

使用$("#id").attr("readonly","true")添加readonly属性

使用$("#id").attr("readonly","false")设置readonly属性失效,但是不管用啊........

最后使用$("#id").removeAttr("readonly")移除该属性后成功

原文链接：https://blog.csdn.net/weixin_38405770/article/details/77847602