Bcrypt 错误：非法参数字符串未识别

Question

here is my complete code这是我的完整代码

var express = require('express'),
    app = express(),
    mongoose = require('mongoose'),
    bodyParser = require('body-parser'),
    morgan = require('morgan'),
    webToken = require('jsonwebtoken'),
    bcrypt = require('bcryptjs'),
    assert = require('assert');
    Schema = mongoose.Schema,
    secretKey = "omjdiuwkslxmshsoepdukslsj";

//User Schema
var userSchema = new Schema({
    username: {type: String, required: true, index: {unique:true}},
    password: {type: String, required: true, select: false}
})

userSchema.pre('save', function(next){
    var user = this;

    if(!user.isModified('password')) return next();

    bcrypt.hash(user.password, null, null, function(err, hash){
        if(err) return next(err);

        user.password = hash;
        next();
    })
});

userSchema.methods.comparePassword = function(password){
    var user = this;

    bcrypt.compare(password, user.password, function(err, result){
        if(err){
            console.log(err);
        }
        else {
            console.log("passwords match!");
            return;
        }
    })
}

var userModel = mongoose.model('users', userSchema);


//Connecting to Mongo
mongoose.connect("mongodb://localhost/userstories", function(err){
    if(err) {
        console.log(err);
    }
    else {
        console.log("Connected to database!");
    }
});

//Creating Token
function createToken(user){
    var token = webToken.sign({
        _id: user.id,
        username: user.username
    },  secretKey,{
        expiresIn: 30 * 60 * 1000
    })
    return token;
    }

//Middlewares
app.use(bodyParser.urlencoded({extended: true}));
app.use(bodyParser.json());
app.use(morgan('dev'));

//Api's

app.post('/signup', function(req, res){    
    var user = new userModel({
        username: req.body.username,
        password: req.body.password
    })

    user.save(function(err){
        if(err){
            console.log(err);
        }

        else{
            res.json({message: "User created!"});
        }
    })
})

app.post('/login', function(req, res){

    userModel.findOne({username: req.body.username}, function(err, user){
        if(err) console.log(err);

            if(!user){
                res.send("User not found!");
            }
                 else if(user){

                      var validPassword = user.comparePassword(req.body.password);

                       if(validPassword){
                                var tokens = createToken(user);

                                res.json({
                                    success: true,
                                    message: "Successfully logged In",
                                    token: tokens
                                });
                        } 

                            else {
                                    res.send("Invalid password");
                                  }

                     }
    })
});


//Running the server
app.listen(3000, function(err){
    if(err) console.log("port not working");
    else{
        console.log("Everything went just fine");
    }
})

I've tried every approaches and saw all the answers here.我已经尝试了所有方法并在这里看到了所有答案。 But no one seem to come across this illegal argument error.但是似乎没有人遇到过这种非法参数错误。 Please figure this one out for me Im sure there is a bug I cant see请帮我弄清楚这个我确定有一个我看不到的错误

Answer 1