CSV File downloads from Node Express server - node.js

Question

I have an API backend with Node and Express. I am trying to take some filtered data from the frontend and create a CSV file and download it for the user. I have been using json2csv. I am able to create the data file correctly and when I use that file in my express route I download a file that just says undefined. At first, I thought it was an asynchronous issue, but after using a setTimeout as a test to see if that was an issue I still get the undefined data file. Console logging the "csvData" shows the correct data.
Express route to download the file.
app.post('/api/downloads/filtered', (req, res) => {
let fields = [];
fields = Object.keys(req.body[0])
const filteredData = req.body;
const json2csvParser = new json2csv({fields: fields});
const csvData = json2csvParser.parse(filteredData);
console.log(csvData)
fs.writeFile('./report.csv', csvData, (err) => {
if (err) {
console.log(err);
}
else {
console.log('created report.csv');
res.download('./report.csv');
}
})
})
I'm using Vue on the frontend, I get the file when clicking a button not sure if that is something I should include.

Answer 1

I ended up figuring out my issue. I found that downloading in a post request didn't seem to be possible. I needed a get request. Since the data for the file came in the request body I ended up keeping the post request to create the file and creating a separate get request to download the file this seemed to work fine but didn't find it documented anywhere so I wasn't sure if a better way exists.
app.post('/api/downloads/filtered', (req, res) => {
console.log(req.body)
let fields = [];
fields = Object.keys(req.body[0])
const filteredData = req.body;
const json2csvParser = new json2csv({fields: fields});
const csvData = json2csvParser.parse(filteredData);
console.log(csvData)
fs.writeFile('./report.csv', csvData, (err) => {
if (err) {
console.log(err);
}
else {
console.log('created report.csv');
}
})
})
app.get('/api/downloads/filtered', (req, res) => {
setTimeout(() => {res.download('./report.csv')}, 1000)
})