当我在使用引导程序时运行这些代码时出现以下错误
练习.js：11 未捕获的类型错误： $(...(。淡出不是函数
我的代码：-
.HTML：
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">
<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/css/bootstrap.min.css" integrity="sha384-ggOyR0iXCbMQv3Xipma34MD+dH/1fQ784/j6cY/iJTQUOhcWr7x9JvoRxT2MZw1T" crossorigin="anonymous">
<link href="https://fonts.googleapis.com/css?family=Roboto+Condensed&display=swap" rel="stylesheet">
<link rel="stylesheet" href="practice.css">
<script type="text/javascript" src="https://code.jquery.com/jquery-2.1.4.js"></script>
<title></title>
</head>
<body>
<div id="effect" class="row my-5">
<div class="col-3"></div>
<div class="col-6">
<img class="img-fluid" src="https://scontent.fjrs1-1.fna.fbcdn.net/v/t1.15752-9/107376723_279529570050364_381202387595922170_n.jpg?_nc_cat=100&_nc_sid=b96e70&_nc_ohc=zXTVBn-CzdsAX_OnKdo&_nc_ht=scontent.fjrs1-1.fna&oh=68eafa443772a6c0d0e773c1d6f794c4&oe=5F2853BC"
alt="">
</div>
<div class="col-3"></div>
</div>
<script src="practice.js"></script>
<script src="https://code.jquery.com/jquery-3.2.1.slim.min.js" integrity="sha384-KJ3o2DKtIkvYIK3UENzmM7KCkRr/rE9/Qpg6aAZGJwFDMVNA/GpGFF93hXpG5KkN" crossorigin="anonymous"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.12.9/umd/popper.min.js" integrity="sha384-ApNbgh9B+Y1QKtv3Rn7W3mgPxhU9K/ScQsAP7hUibX39j7fakFPskvXusvfa0b4Q" crossorigin="anonymous"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/js/bootstrap.min.js" integrity="sha384-JZR6Spejh4U02d8jOt6vLEHfe/JQGiRRSQQxSfFWpi1MquVdAyjUar5+76PVCmYl" crossorigin="anonymous"></script>
</body>
</html>JavaScript ：
$("#effect").on("click", function() {
$(this).fadeOut();
});
你正在加载jQuery两次。
首先，加载jquery-2.1.4.js(已过时，存在已知的安全问题，不应使用(。
然后你加载jquery-3.2.1.slim.min.js(这是过时的，等等，不包括你尝试使用的效果模块！
加载 jQuery一次，使其成为当前版本 (3.5.1(，如果您需要不包含的功能，请不要使用精简版本。
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<html>
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">
<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/css/bootstrap.min.css" integrity="sha384-ggOyR0iXCbMQv3Xipma34MD+dH/1fQ784/j6cY/iJTQUOhcWr7x9JvoRxT2MZw1T" crossorigin="anonymous">
<link href="https://fonts.googleapis.com/css?family=Roboto+Condensed&display=swap" rel="stylesheet">
<link rel="stylesheet" href="practice.css">
<title></title>
</head>
<body>
<div id="effect" class="row my-5">
<div class="col-3"></div>
<div class="col-6">
<img class="img-fluid" src="https://scontent.fjrs1-1.fna.fbcdn.net/v/t1.15752-9/107376723_279529570050364_381202387595922170_n.jpg?_nc_cat=100&_nc_sid=b96e70&_nc_ohc=zXTVBn-CzdsAX_OnKdo&_nc_ht=scontent.fjrs1-1.fna&oh=68eafa443772a6c0d0e773c1d6f794c4&oe=5F2853BC"
alt="">
</div>
<div class="col-3"></div>
</div>
<button class="btn1">Fade out</button>
<button class="btn2">Fade in</button>
<script src="practice.js"></script>
<script>
$(".btn1").click(function(){
$("img").fadeOut();
});
$(".btn2").click(function(){
$("img").fadeIn();
});
</script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.12.9/umd/popper.min.js" integrity="sha384-ApNbgh9B+Y1QKtv3Rn7W3mgPxhU9K/ScQsAP7hUibX39j7fakFPskvXusvfa0b4Q" crossorigin="anonymous"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/js/bootstrap.min.js" integrity="sha384-JZR6Spejh4U02d8jOt6vLEHfe/JQGiRRSQQxSfFWpi1MquVdAyjUar5+76PVCmYl" crossorigin="anonymous"></script>
</body>
</html>