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_forfrom flask_sqlalchemy import SQLAlchemyimport configapp = 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)db.create_all()@app.route('/')def home():    return render_template('index.html')@app.route('/signin/',methods=['GET','POST'])def sign_in():    return render_template('denglu1.html')

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

@app.route('/question/') def question(): return render_template('question.html') if __name__ == '__main__': app.run(debug=True)

function fnLogin(){            var oNewname = document.getElementById("uname");            var oNewpass = document.getElementById("upass");            var oAgainname = document.getElementById("aupass");            var oError = document.getElementById("error_box");            var isError=true;            oError.innerHTML="
"            if(oNewname.value.length<6 && oNewname.value.length>12) {                oError.innerHTML = "用户名需在6-12位中间";                isError=false;                return isError;            }           else if ((oNewname.value.charCodeAt(0)>=48)&&(oNewname.value.charCodeAt(0)<=57)){                oError.innerHTML ="用户名开头不能为数字";               isError=false;                return isError;            }            else for(var i=0;i
      
       57)&&(oNewname.value.charCodeAt(i)<97 || oNewname.value.charCodeAt(i)>122)){                    oError.innerHTML = "用户名只能为数字或字母";                   isError=false;                   return isError;                }                }            //密码            if(oNewpass.value.length>12|| oNewpass.value.length<6){                oError.innerHTML="密码需在6-12位中间";               isError=false;                return isError;            }            else if(oNewpass.value != oAgainname.value) {                oError.innerHTML="两次密码输入不一致";               isError=false;                return isError;            }            window.alert("注册成功！")        }
      

{% extends'index.html' %}{% block head %}    
          {% endblock %}{% block main %}
      
  
       
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{% endblock %}