我为jQuery UI添加了日期选择器，但出现了此错误：
未捕获的TypeError：$（...）。datepicker不是函数
我添加了插件jQuery和jQuery-ui，但是我也有错误
细枝：
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8" />
<title>{% block title %}Acceuil-{% endblock %}</title>
{% block stylesheets %}
<link href="https://fonts.googleapis.com/css?family=Open+Sans:400,700|Raleway:400,700|Merriweather:400,700" rel="stylesheet" type="text/css">
<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/font-awesome/4.7.0/css/font-awesome.min.css">
<link href="https://unpkg.com/leaflet@1.0.3/dist/leaflet.css" rel="stylesheet">
<link rel="stylesheet" href="{{ asset('bundles/app/css/MarkerCluster.css') }}">
<link rel="stylesheet" href="{{ asset('bundles/app/css/MarkerCluster.Default.css') }}">
<link rel="stylesheet" href="{{ asset('bundles/app/css/application-42e4eacdbf0506bba5a7d1c783732309c84eb2d6203203da608691b414ebe1c7.css') }}">
{% endblock %}
<link rel="icon" type="image/x-icon" href="{{ asset('favicon.ico') }}" />
</head>
<body>
<div id="page">
{% block header %}
<header id="navbar">
<div class="container">
<a class="logo nounou-top" href="{{path('homePage')}}">BabySitter</a>
<div class="ui secondary user menu floated right">
<div id="connect_subscribe_links">
<a class="item" id="navbar_connect" href="{{path('fos_user_security_login')}}">Connexion</a>
<a class="ui small action button blue" id="navbar_subscribe" href="{{ path('inscription') }}">Inscription</a>
</div>
<div class="ui dropdown autolaunch icon button right top pointing blue" id="connect_subscribe_menu">
<i class="dropdown icon"></i>
<div class="ui menu transition hidden">
<a class="item" href="/sessions/new">Connexion</a>
<a class="item" href="/welcome/choice_category_ad">Inscription</a>
</div>
</div>
</div>
</div>
</header>
{% endblock %}
{% block body %}
{% endblock %}
</div>
{% block javascripts %}
<script src="{{ asset('bundles/app/js/places.js') }}"></script>
<script src="{{ asset('bundles/app/js/jquery.js') }}"></script>
<script src="{{ asset('bundles/app/js/jquery-ui.min.js') }}"></script>
<script src="{{ asset('bundles/app/js/application-5385288a7f4b3693dff01f301b0b54547c2887a2eaf0c85b91ed655ec7424ff7.js') }}"></script>
<script src="{{ asset('bundles/app/js/stripe.js') }}"></script>
<script>
$( function() {
$( "#datepicker" ).datepicker();
} );
</script>
{% endblock %}
</body>
</html>
我添加了插件jquery和jquery UI，但是我有此错误..如何解决此错误