1. 用url_for加载静态文件
    1. <script src="{{ url_for('static',filename='js/login.js') }}"></script>
    2. flask 从static文件夹开始寻找
    3. 可用于加载css, js, image文件
  2. 继承和扩展
    1. 把一些公共的代码放在父模板中，避免每个模板写同样的内容。base.html
    2. 子模板继承父模板
      1.   {% extends 'base.html’ %}
    3. 父模板提前定义好子模板可以实现一些自己需求的位置及名称。block
      1. <title>{% block title %}{% endblock %}-MIS问答平台</title>
      2. {% block head %}{% endblock %}
      3. {% block main %}{% endblock %}
    4. 子模板中写代码实现自己的需求。block
      1.   {% block title %}登录{% endblock %}
  3. 首页、登录页、注册页都按上述步骤改写。
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>
        {% block title %}Home
        {% endblock %}
        </title>

 <link rel="stylesheet" type="text/css" href="{{ url_for("static", filename="ch22.css") }}">
  <script src="{{ url_for('static',filename='moshi.js') }}"></script>
{% block head %}
{% endblock %}



</head>
<body>

<nav>




    <a href="http://127.0.0.1:5000/">首页</a>
    <a href="http://127.0.0.1:5000/login">登录</a>
    <a href="{{ url_for('register') }}">注册</a>
    <a href="{{ url_for('question') }}">发布问题</a>
         <a href="">音乐</a>
         <a href="">电影</a>
         <input type="text" name="search1">
         <button type="submit">搜索</button>
        <a href="" >加入我们</a>

    <img onclick="mySwitch()" id="on_off" src="{{ url_for('static',filename='on.jpg') }}" width="20px">
</nav>
{% block main %}
{% endblock %}
 <p id="a"> <br> <br> <br>常见问题</p><p class="textblue">联系我们</p><p>用户意见</p>


</body>
</html>
{% extends 'base.html' %}
{% block title %}
    登录
{% endblock %}

{% block head %}
    <link rel="stylesheet" type="text/css" href="{{ url_for("static", filename="ch11.css") }}">

     <script src="{{ url_for('static',filename='js123.js') }}"></script>
{% endblock %}

{% block main %}
 <section class="container">
    <div class="login" >

          <h1>登录</h1>


        <p><input id="umane"type="text"placeholder="请输入用户名"></p>


        <p><input id="upass"type="password"placeholder="请输入密码"></p>

          <div id="error_box"><br></div>
<p class="submit">

    <input  onclick="myLogin()" type="submit" name="commit" value="登录">
     <input  onclick=window.alert("是否取消登录？") type="submit" name="commit" value="取消">
</p>
    </div>
           </section>
</div>
</body>
{% endblock %}
{% extends 'base.html' %}
{% block title %}
    注册
{% endblock %}

{% block head %}
 <link rel="stylesheet" type="text/css" href="{{ url_for("static", filename="ch11.css") }}">

   <script src="{{ url_for('static',filename='js1234.js') }}"></script>
{% endblock %}

{% block main %}
 <section class="container">
    <div class="login">

          <h1>注册</h1>


        <p><input id="unane"type="text"placeholder="请输入账户"></p>


        <p><input id="upass"type="password"placeholder="请输入密码"></p>
       <p><input id="upass1"type="password"placeholder="请再次输入密码"></p>
          <div id="error_box"><br></div>
<p class="submit">

    <input  onclick="myLogin()" type="submit" name="commit" value="注册">
     <input  onclick=window.alert("是否取消注册？") type="submit" name="commit" value="取消">
</p>
    </div>
           </section>
</div>
</body>
{% endblock %}