在CRUD中创建发布请求时出现问题

Question

这是我的代码：

//server.js
const express = require('express'),
cors = require('cors'),
bodyParser = require('body-parser'),
mongoose = require('mongoose');

const Mate = require('./models/mate');

mongoose.Promise = global.Promise;

const app = express();
const router = express.Router();
app.use(cors());
app.use(bodyParser.json())
mongoose.connect('mongodb://localhost:27018/mate', {useNewUrlParser: true});
const connection = mongoose.connection;
connection.once('open', () => {
console.log('Mongodb db connection established succ');
})
router.route('/mate').get((req, res) => {
mongoose.model('Mate').find((err, mate) =>  {
if (err) 
console.log(err);
else
res.json(mate);
});
});
router.route('/mate/:id').get((req, res) => {
mongoose.model('Mate').findById((err, mate) => {
if(err)
console.log(err);
else
res.json(mate);
});
});
router.route('/mate/add').post(async (req, res) => {
try {
const mate = new Mate(req.body);
await mate.save();
res.status(200).json({
'mate:': 'Added succesfully'
});
} catch (err) {
console.log(err);
res.status(400).send( 'failed to create' );
}
}); 
router.route('mate/update/:id').post((req, res) => {
mongoose.model(Mate).findById(req.params.id, (err, mate) =>{
if(!mate)
return next(new Error('couldnt load doc'))
else {
mate.title = req.body.title;
mate.day = req.body.day;
mate.severity = req.body.severity;
mate.status = req.body.status;
mate.save().then(mate => {
res.json('Update done');
}).catch(err => {
res.status(400).send('update failed');
});
}
});
});
router.route('mate/delete/:id').get((req, res) => {
mongoose.model(Mate).findByIdAndRemove({_id: req.params.id}, (err, mate) => {
if(err)
res.json(err);
else
res.json('Removed');
});
});
app.use('/', router);
app.listen(4000, () => console.log('server running on port 4000'));
//mate.js
const mongoose = require('mongoose')
const Schema = mongoose.Schema;
let MateSchema = new Schema({
title: {
type: String
},
day: {
type: String
},
severity: {
type: String
},
status: {
type: String, 
default: 'Open'
}
});
module.export = mongoose.model('Mate', MateSchema);

所以基本上问题是在server.js中添加控制器，它必须在创建了新json的情况下向我的DB抛出post请求。嗯，它没有，但它抛出了这个错误：TypeError:Mate不是构造函数；

请帮我弄清楚为什么会这样。我是代码新手，所以这可能是个愚蠢的问题，但我一直在努力。

Answer 1

让mate.js像下面的一样

module.exports = function(mongoose) {
var options = {
collection: 'mate',
timestamps: {
createdAt: 'created_on',
updatedAt: 'updated_on'
},
toObject: {
virtuals: true
},
toJSON: {
virtuals: true
}
};
let MateSchema = new mongoose.Schema({
title: {
type: String
},
day: {
type: String
},
severity: {
type: String
},
status: {
type: String, 
default: 'Open'
}
});

return MateSchema;
};

Answer 2

将模块导出更改为：

module.export = Mate = mongoose.model('Mate', MateSchema);