<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script src="../js/jquery-3.5.1.js"></script>
    <script>
        $(function () {
            //表单 伪类选择器
            //：checkbox
           //$("input:checkbox").attr("checked","true");
            $("input:checkbox").attr("checked","checked");
        });
    </script>
</head>
<body>
    <p>性别：
        <input type="radio" name="gendar" id="sex_man">
        <label for="sex_man">男</label>
        <input type="radio" name="gendar" id="sex_woman">
        <label for="sex_woman">女</label>
    </p>
    <p>喜欢的水果：
        <input type="checkbox" id="apple"><label for="apple">苹果</label>
        <input type="checkbox" id="watermelon"><label for="watermelon">西瓜</label>
        <input type="checkbox" id="peach"><label for="peach">蜜桃</label>
    </p>
</body>
</html>