完成注册功能

1. js文件： onclick函数return True时才提交表单，return False时不提交表单。
2. html文件：
   1. <form>中设置 action和method="post"
   2. <input> 中设置 name
3. 主py文件中：
   1. from flask import  request, redirect, url_for
   2. @app.route('/regist/', methods=['GET', 'POST’])

def regist():

   if request.method == 'GET':

        return render_template('regist.html')

   else:

        username = request.form.get(‘username’)#获取form中的数据

        判断用户名是否存在

        存到数据库中

        redirect重定向到登录页

function fnzhuce() {
    var oUname = document.getElementById("uname");
    var oUpass = document.getElementById("upass");
    var oUpass1 = document.getElementById("upass1");
    var oError = document.getElementById("error_box");
    oError.innerHTML = "<br>";
    if (oUname.value.length < 6 || oUname.value.length > 20) {
        oError.innerHTML = "用户名要6-20之位";
        return;
    } else if ((oUname.value.charCodeAt(0) >= 48) && (oUname.value.charCodeAt(0) <= 57)) {
        oError.innerHTML = "首字母不能为数字";
        return;
    } else for (var i = 0; i < oUname.value.length; i++) {
        if ((oUname.value.charCodeAt(i) < 48) || (oUname.value.charCodeAt(i) > 57) && ((oUname.value.charCodeAt(i) < 97)) || oUname.value.charCodeAt(i) > 122) {
            oError.innerHTML = "只能填写数字或字母";
            return;
        }
    }
// oUpass
    if (oUpass.value.length < 6 || oUpass.value.length > 20) {
        oError.innerHTML = "密码要6-20位";
        return;
    }
    else if (oUpass.value !== oUpass1.value) {
        oError.innerHTML = "两次密码不一致";
        return false;
    }
    return true;
    window.alert("注册成功")

}

{% extends 'daohang.html' %}
{% block title %}注册{% endblock %}
{% block head %}
    <link rel="stylesheet" type="text/css" href="{{ url_for('static',filename='css/zhuce.css') }}">
    <script src="{{ url_for('static',filename='js/zhuce.js') }}"></script>
{% endblock %}

{% block main %}
    <div class="box">
        <h2>注册</h2>
        <form action="{{ url_for('zhuce') }}" method="post">
            <div class="input_box">
                <input id="uname" type="text" placeholder="请输入用户名" name="username">
            </div>
            <div class="input_box">
                <input id="upass" type="password" placeholder="请输入密码" name="password">
            </div>
            <div class="input_box">
                <input id="upass1" type="password" placeholder="请再次输入密码">
            </div>
            <div id="error_box"><br></div>
            <div class="input_box">
                <button onclick="fnzhuce()">注册</button>
            </div>
        </form>
    </div>
{% endblock %}

@app.route('/zhuce/', methods=['GET', 'POST'])
def zhuce():
    if request.method == 'GET':
        return render_template('zhuce.html')
    else:
        username = request.form.get('username')
        password = request.form.get('password')
        user = User.query.filter(User.username == username).first()
        if user:
            return 'username existed'
        else:
            user = User(username=username, password=password)
            db.session.add(user)  # 数据库操作
            db.session.commit()
            return redirect(url_for('denglu'))