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,sessionfrom flask_sqlalchemy import SQLAlchemyimport configapp = Flask(__name__)app.config.from_object(config)db=SQLAlchemy(app)db = SQLAlchemy(app)# 创建用户模型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)#db.create_all()@app.route('/')def homepage():    return render_template("homepage.html")@app.route('/login/')def login():    return render_template("login.html")@app.route("/register/",methods=['GET','POST'])def register():    if request.method == "GET":        return render_template("register.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)            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)

{% extends'index.html' %} {% block title %}     注册        {% endblock %}{% block head %}    
         {% endblock %}{% block main %}
     
    
      
       
欢迎注册
      
    
      
        
       
                    账号　     
           
       
       
        
       
                    密码　     
        
       
       
         
       
                    再输入     
        
       
       
        
       
        
       
         
       
            
        注册
       
    
      
     
{% endblock %}

function fnLogin() {        var uname = document.getElementById("name")        var uError = document.getElementById("error_box")        var upassword = document.getElementById("password")        var upasswordagain = document.getElementById("passwordagain")        var isError =true;         if(uname.value.length<6 || uname.value.length >20){        uError.innerHTML="用户名应为6到20字符";        isError = false;         return;    }else if ((uname.value.charCodeAt(0)>=48) && (uname.value.charCodeAt(0)<=57)){        uError.innerHTML="第一位只能是字母";        isError = false;        return ;    } else for (var i=0 ; i
     
      57)&&(uname.value.charCodeAt(i)<97)|| uname.value.charCodeAt(i)>122){            uError.innerHTML="用户名只能为数字或者字母";           isError = false;         return;        }    }    if(upassword.value.length<6 || upassword.value.length>12){        uError.innerHTML="密码应为6到20字符";       isError = false;         return;    }    if (upasswordagain.value!=upassword.value ) {        uError.innerHTML = "重新输入你的密码";       isError = false;         return;    }    return isError;    window.alert("注册成功")}