<html>
    <head>
        <meta charset=utf-8>
    </head>
    <body>
        <form>
            <label>牛客会陪伴大家</label>
            <input id="checkbox" type="checkbox" checked />
        </form>
    </body>
    <script type="text/javascript">
        // 补全代码
        var item = document.querySelector("#checkbox")
        item.onclick = function(e){
            e.preventDefault()
        }
    </script>
</html>