jQuery事件4-3练习

来源：4-3 编程练习

深海皮皮虾

2019-06-09 15:12:18

<!DOCTYPE html>
<html>

<head>
    <meta charset="UTF-8">
    <title>习题</title>
</head>

<body>
    <input type="text" value=""><span></span>
    <script src="https://cdn.bootcss.com/jquery/3.3.1/jquery.js"></script>
    <script>
        $(document).ready(function() {
            
            $("input").focus(function() {
                $("span").text("请输入用户名");
            })
            
            $("input").blur(function() {
                if($("input").val() == "") {
                    $("span").text("用户名不能为空");
                    $(this).css({"border-color": "red"});
                } else {
                    $("span").text("");
                    $(this).css({"border-color": "green"});
                }
                
            })
        })
   
    </script>
</body>

</html>

请老师检查

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