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:存在报错

  不存在，存到数据库中

       redirect重定向到登录页

from flask import Flask,render_template,request,redirect,url_for,session
from flask_sqlalchemy import SQLAlchemy

import config
app = Flask(__name__)
app.config.from_object(config)
db = SQLAlchemy(app)

class User(db.Model):
    __tablename__ = 'user'
    id = db.Column(db.Integer,primary_key=True,autoincrement=True)
    username = db.Column(db.String(20),nullable=False)
    password = db.Column(db.String(20), nullable=False)
    nickname = db.Column(db.String(20))

#db.create_all()


@app.route('/')
def index():
    return render_template('base.html')

@app.route('/login/')
def login():
    return render_template('login.html')

@app.route('/regist/',methods=['GET','POST'])
def regist():
    if request.method=='GET':
        return render_template('regist.html')
    else:
        usern=request.form.get('username')
        nickn=request.form.get('nickname')
        passw=request.form.get('password')
        user=User.query.filter(User.username==usern).first()
        if user:
            return u'username existed.'
        else:
            user1=User(username=usern,password=passw,nickname=nickn)
            db.session.add(user1)
            db.session.commit()
            return  redirect(url_for('login'))

@app.route('/question/')
def question():
    return render_template('question.html')

if __name__ == '__main__':
    app.run(debug=True)

　　#regist.html

{% extends 'base.html' %}
{% block title %}Regist{% endblock %}

{% block head %}
    <link href="{{ url_for('static',filename='css/js31.css') }}" rel="stylesheet" type="text/css">
    <script src="{{ url_for('static',filename='js/regist.js') }}"></script>
{% endblock %}

{% block main %}
    <div class="box">
            <h2>注册页面</h2>
            <form action="{{ url_for('regist') }}" method="post">
            <div class="input_box">
                输入用户名： <input id="uname" type="text" placeholder="请输入用户名" name="username"></div>
                <div class="input_box">
                     昵称：<input id="unickname" type="text" placeholder="昵称" name="nickname">
        </div>
             <div class="input_box">
                 输入密码： <input id="upass" type="password" placeholder="请输入密码" name="password"></div>
                <div class="input_box">
                确认密码： <input id="checkpass" type="password" placeholder="请确认密码">
             </div>
        <div id="error_box"><br></div>
        <div class="input_box">
            <button onclick="fnRegist()">注册</button>
            <button onclick=window.alert("此页面询问您是否要离开：您输入的数据可能不会被保存")>取消</button></div>
            </form>
    </div>
{% endblock %}

　　#regist.js

function fnRegist() {
    var oPass=document.getElementById("upass").value;
    var oPass1=document.getElementById("checkpass").value;

    if(oPass!=oPass1){
        document.getElementById("error_box").innerHTML="两次密码不一致！";
        return false;
    }
    return true;
}