Node.js mongoose模式上未定义的字段

我得到一个未定义的字段，试图比较用户密码

这就是函数

logUser = (req,res) => {
       User.findOne({ username:req.body.username}, (err,user) => {
            if(!user){
                req.flash('error','El nombre de usuario no existe');
                res.redirect('/login');
            }else if(!user.comparePassword(req.body.password)){
                req.flash('error','La contraseña no es correcta');
                res.redirect('/login');
            }else{
                res.redirect('/');
            }
       });
    }

当执行转到else if并使用comparePassword函数时，架构字段未定义

模式文件

const mongoose = require('mongoose');
const Schema = mongoose.Schema;
const bcrypt = require('bcrypt');

const userSchema = Schema({
    username:String,
    email:String,
    password:String,
    registrationDate: {type:Date, defaul: Date.now()}
});

userSchema.methods.encryptPassword = (password) =>{
    return bcrypt.hashSync(password, bcrypt.genSaltSync(10));
}

userSchema.methods.comparePassword = (password) =>{
    console.log('password: ',this.password);
    return bcrypt.compareSync(password, this.password);//here this.password is undefined
}

module.exports = mongoose.model('User',userSchema)

---

调试时我看到用户对象不是schem类，tuis类的作用是什么？

简而言之，如果替换

userSchema.methods.comparePassword = (password) =>{
    console.log('password: ',this.password);
    return bcrypt.compareSync(password, this.password);//here this.password is undefined
}

与

由于arrow函数的词法作用域，您面临着这个问题。箭头函数从父函数继承其此作用域

userSchema.methods.comparePassword = function(password) {
    console.log('password: ',this.password);
    return bcrypt.compareSync(password, this.password);//here this.password is undefined
}