使用GET定义相同的常量，而使用POST定义未定义的常量-express，mongo，react

我正在关注一个React教程，其中我正在MERN堆栈中构建一个基本博客。

In this particular case, in my Server.js file I am attempting a POST request to MongoDB. It identifies the collection & JSON object using URL parameters, alters the object & returns a new constant equal to the new object.

The issue is that the const equal to the object found is showing to be not defined. However, I cannot figure out why that would be. Another function using a GET request with the same const (each are local to their respective functions) works as designed with no error regarding defining the const.

import express from 'express';
import bodyParser from 'body-parser';
import { MongoClient } from 'mongodb';

const app = express();

// also tried to use express' built in bodyparser, same error
app.use(bodyParser.json());

// working GET req function using the same const
app.get('/api/articles/:name', async (req,res) => {
    try {
        const articleName = req.params.name;

        const client = await MongoClient.connect('mongodb://localhost:27017', { useNewUrlParser: true });
        const db = client.db('my-app-db');

// this is the const in question, equal to object found
// based on name param passed in URL
        const articleInfo = await db.collection('articles').findOne({ name: articleName });
        res.status(200).json(articleInfo);

        console.log(articleInfo);

        client.close();
    } catch (error) {
        res.status(500).json({message: 'Error connecting to db', error});
    }
    
});

// non working POST req function, using the same const
app.post('api/articles/:name/upvote', async (req,res) => {
    try {
        const articleName = req.params.name;

        const client = await MongoClient.connect('mongodb://localhost:27017', { useNewUrlParser: true });
        const db = client.db('my-app-db');
        
        // gets error for being undefined at Server.js 32:5
        const articleInfo = await db.collection('articles').findOne({ name: articleName });
        await db.collection('articles').updateOne({ name: articleName },{
            '$set' : {
                upvotes: articleInfo.upvotes + 1,
            }, 
        });
        
        // this is updated article sent as response 
        const updatedArticleInfo = await db.collection('articles').findOne({ name: articleName });

        res.status(200).json(updatedArticleInfo);
        client.close();

    } catch (error) {
        res.status(500).json({message: 'Error connecting to db', error});
    }
})

app.listen(8000, () => console.log('Listening on port 8000'));

这是与邮递员收到的错误完全相同的错误

ReferenceError：未定义articleInfo      在C：\ Users \ oduboise \ Desktop \ sandbox \ react-full-stack \ my-app-backend \ src / Server.js：32：5      在Layer.handle上[作为handle_request]（C：\ Users \ oduboise \ Desktop \ sandbox \ react-full-stack \ my-app-backend \ node_modules \ express \ lib \ router \ layer.js：95：5）      在下一个（C：\ Users \ oduboise \ Desktop \ Sandbox \ react-full-stack \ my-app-backend \ node_modules \ express \ lib \ router \ route.js：137：13）      在Route.dispatch（C：\ Users \ oduboise \ Desktop \ sandbox \ react-full-stack \ my-app-backend \ node_modules \ express \ lib \ router \ route.js：112：3）      在Layer.handle上[作为handle_request]（C：\ Users \ oduboise \ Desktop \ sandbox \ react-full-stack \ my-app-backend \ node_modules \ express \ lib \ router \ layer.js：95：5）      在C：\ Users \ oduboise \ Desktop \ Sandbox \ react-full-stack \ my-app-backend \ node_modules \ express \ lib \ router \ index.js：281：22      在参数下（C：\ Users \ oduboise \ Desktop \ sandbox \ react-full-stack \ my-app-backend \ node_modules \ express \ lib \ router \ index.js：354：14）      在参数上（C：\ Users \ oduboise \ Desktop \ sandbox \ react-full-stack \ my-app-backend \ node_modules \ express \ lib \ router \ index.js：365：14）      在Function.process_params（C：\ Users \ oduboise \ Desktop \ sandbox \ react-full-stack \ my-app-backend \ node_modules \ express \ lib \ router \ index.js：410：3）      在下一个（C：\ Users \ oduboise \ Desktop \ Sandbox \ react-full-stack \ my-app-backend \ node_modules \ express \ lib \ router \ index.js：275：10）

This is the response from the successful GET request, as a JSON object

{
"_id": "5ec60f1390d2ce923cdb0e41",
"name": "what-react",
"upvotes": 0,
"comments": []
}

这也是我第一次在StackOverflow中提出问题，通常我能够弄清楚/找到它。因此，任何问题格式提示也将不胜感激