Error: Illegal arguments: undefined string at bcrypt.hashSync

用react写后端的signUp时出现报错undefined string at bcrypt.hashSync，代码如下，报错在生成password时！

const bcrypt = require('bcryptjs')
const jwt = require('jsonwebtoken')
const db = require('../config/db.config.js')
const User = db.user
const errorHandler = require('../utils/errorHandler')

module.exports.register = async function(req, res) {
    const candidate = await User.findOne({
        where: {
            username: req.body.username
        }
    })

    if (candidate) {
        res.status(409).json({
            message: 'This login is already taken. Try another.'
        })
    } else {
        const salt = bcrypt.genSaltSync(10)
        const password = req.body.password
        const user = new User({
            name: req.body.name,
            username: req.body.username,
            roles: req.body.roles,
            photoSrc: req.file ? req.file.path: '',
            password: bcrypt.hashSync(password, salt)
        })
        try {
            await user.save()
            res.status(201).json(user)
        } catch(e) {
            errorHandler(res, e)
        }
    }
}

修改方式，在生成salt和password时，使用await，因为本身就是异步运行：

const salt = await bcrypt.genSaltSync(10);
const password = await req.body.password;