I made a mistake when I joined cookies. I can't load the page. - Codes Helper

Ajax code of the front end:

/**
 * Created by Administrator on 2018/4/17.
 */

$(function() {

    var $loginBox = $("-sharploginBox");
    var $registerBox = $("-sharpregisterBox");
    var $userInfo = $("-sharpuserInfo");

    //
    $loginBox.find("a.colMint").on("click", function() {
        $registerBox.show();
        $loginBox.hide();
    });

    //
    $registerBox.find("a.colMint").on("click", function() {
        $loginBox.show();
        $registerBox.hide();
    });

    //
    $registerBox.find("button").on("click", function() {
        //ajax
        $.ajax({
            type: "post",
            url: "/api/user/register",
            data: {
                username: $registerBox.find("[name="username"]").val(),
                password: $registerBox.find("[name="password"]").val(),
                repassword:  $registerBox.find("[name="repassword"]").val()
            },
            dataType: "json",
            success: function(result) {
                $registerBox.find(".colWarning").html(result.message);
                if (!result.code) {
                    //
                    setTimeout(function() {
                        $loginBox.show();
                        $registerBox.hide();
                    }, 1000);
                }

            }
        });
    });

    //
    $loginBox.find("button").on("click", function() {
        //ajax
        $.ajax({
            type: "post",
            url: "/api/user/login",
            data: {
                username: $loginBox.find("[name="username"]").val(),
                password: $loginBox.find("[name="password"]").val()
            },
            dataType: "json",
            success: function(result) {

                $loginBox.find(".colWarning").html(result.message);

                if (!result.code) {
                    //
                    setTimeout(function() {
                        window.location.reload();
                    }, 1000);
                }
            }
        })
    })

    //
    $("-sharplogout").on("click", function() {
        $.ajax({
            url: "/api/user/logout",
            success: function(result) {
                if (!result.code) {
                    window.location.reload();
                }
            }
        });
    })

})

app.js of backend

/**
 * Created by Administrator on 2018/4/16.
 * 
 */
//express
var express = require("express");
//
var swig = require("swig");
//
var mongoose = require("mongoose");
//body-parserpost
var bodyParser = require("body-parser");
//cookies
var cookieParser = require("cookie-parser")
//app=>NodeHS Http.createServer()
var app = express();

//
//url/public__dirname + "/public"
app.use("/public", express.static(__dirname + "/public"));
// app.use("/static", express.static("public"));

//
//
//
app.engine("html", swig.renderFile);
//views
app.set("views", "./views");
/*view engineapp.engine*/
app.set("view engine", "html");
//
swig.setDefaults({cache: false});

//bodyparser
app.use( bodyParser.urlencoded({extended:true}) );

app.use( function(req, res, next) {
    req.cookies = new cookieParser(req, res);

    //cookie
    req.userInfo = {};
    if (req.cookies.get("userInfo")) {
        try {
            req.userInfo = JSON.parse(req.cookies.get("userInfo"));

            //
            User.findById(req.userInfo._id).then(function(userInfo) {
                req.userInfo.isAdmin = Boolean(userInfo.isAdmin);
                next();
            })
        }catch(e){
            next();
        }

    } else {
        next();
    }
} );

/*
 * 
 * */
app.use("/admin", require("./routers/admin"));
app.use("/api", require("./routers/api"));
app.use("/", require("./routers/main"));

//http
mongoose.connect("mongodb://localhost:27017/blog",function (err) {
    if(err){
        console.log("");
    }else{
        console.log("");
        app.listen(8081);
    }
});
// app.listen(8081);

api.js

/**
 * Created by Administrator on 2018/4/16.
 */

var express = require("express");
var router = express.Router();
var User = require("../models/User");
//
var responseData;

router.use(function (req, res, next) {
    responseData = {
        code: 0,
        message:""
    }

    next();
});
/*
* 
* 
*
* 1.
* 2.
* 3.
* 
* 1.
*   
* */
router.post("/user/register", function (req, res, next) {
    var username = req.body.username;
    var password = req.body.password;
    var repassword = req.body.repassword;


    //
    if(username == ""){
        responseData.code = 1;
        responseData.message = "";
        res.json(responseData);
        return;
    }
    //
    if(password == ""){
        responseData.code = 2;
        responseData.message = "";
        res.json(responseData);
        return;
    }
    //   
    if(password != repassword){
        responseData.code = 3;
        responseData.message = "";
        res.json(responseData);
        return;
    }


    //
    User.findOne({
        username: username
    }).then(function (userInfo) {
        if( userInfo){
            //
            responseData.code = 4;
            responseData.message = ""
            res.json(responseData);
            return;
        }
        //
        var user = new User({
            username: username,
            password: password
        });
        return user.save();
    }).then(function (newUserInfo) {
        responseData.message = "";
        res.json(responseData);
    });

});

router.post("/user/login", function (req, res, next) {
    var username = req.body.username;
    var password = req.body.password;

    if( username == ""|| password ==""){
        responseData.code = 1;
        responseData.message = "";
        res.json(responseData);
        return;
    }

    //
    User.findOne({
        username: username,
        password: password
    }).then(function (userInfo) {
        if(!userInfo){
            responseData.code = 2;
            responseData.message = "";
            res.json(responseData);
            return;
        }
        //
        responseData.message = "";
        responseData.userInfo = {
            _id: userInfo._id,
            username: userInfo.username
        }
        req.cookies.set("userInfo", JSON.stringify({
            _id: userInfo._id,
            username: userInfo.username
        }));
        res.json(responseData);
        return;
    })
});

/*
 * 
 * */
router.get("/user/logout", function(req, res) {
    req.cookies.set("userInfo", null);
    res.json(responseData);
});

module.exports = router;

error reporting problem:

TypeError: req.cookies.get is not a function
    at D:\WorkSpace\WebStorm\project\app.js:42:21
    at Layer.handle [as handle_request] (D:\WorkSpace\WebStorm\project\node_modules\express\lib\router\layer.js:95:5)
    at trim_prefix (D:\WorkSpace\WebStorm\project\node_modules\express\lib\router\index.js:317:13)
    at D:\WorkSpace\WebStorm\project\node_modules\express\lib\router\index.js:284:7
    at Function.process_params (D:\WorkSpace\WebStorm\project\node_modules\express\lib\router\index.js:335:12)
    at next (D:\WorkSpace\WebStorm\project\node_modules\express\lib\router\index.js:275:10)
    at urlencodedParser (D:\WorkSpace\WebStorm\project\node_modules\body-parser\lib\types\urlencoded.js:91:7)
    at Layer.handle [as handle_request] (D:\WorkSpace\WebStorm\project\node_modules\express\lib\router\layer.js:95:5)
    at trim_prefix (D:\WorkSpace\WebStorm\project\node_modules\express\lib\router\index.js:317:13)
    at D:\WorkSpace\WebStorm\project\node_modules\express\lib\router\index.js:284:7
    at Function.process_params (D:\WorkSpace\WebStorm\project\node_modules\express\lib\router\index.js:335:12)
    at next (D:\WorkSpace\WebStorm\project\node_modules\express\lib\router\index.js:275:10)
    at expressInit (D:\WorkSpace\WebStorm\project\node_modules\express\lib\middleware\init.js:40:5)
    at Layer.handle [as handle_request] (D:\WorkSpace\WebStorm\project\node_modules\express\lib\router\layer.js:95:5)
    at trim_prefix (D:\WorkSpace\WebStorm\project\node_modules\express\lib\router\index.js:317:13)
    at D:\WorkSpace\WebStorm\project\node_modules\express\lib\router\index.js:284:7