How to download a generated csv file from backend in the client side

Question

I am using ejs and node. On a button press there I am generating a csv file containing some information. I want to download that in the client side. This is the code I am trying but its not working.

app.post('/', async(req, res) => {

console.log('triggerd');
console.log('req', req.body);
const url= req.body.url;
await scrapeData(url);
const file = `${__dirname}/companies1.csv`;
res.download(file); // Set disposition and send it.
res.redirect('/')

})

Please help if possible.

Answer 1

Firstly, if you want to retrieve data from your backend, you should use a get request and not a post request. Post requests are for sending data from front to back, and get requests for sending data from back to end.

Secondly, if you want to send a file from your node.js server, you can use the following method :

const fs = require('fs');
fs.readFile(pathToYourFile, async (error: Error, data: any) => {
                    if (error) return console.log(error);
                    res.write(data, 'binary');
                    res.status(200).end(null, 'binary');
                });

This will return a binary value of your file, that you will have to convert to a string and then to a file, using a function such as this (this one is in angular/typescript, I don't really know if it applies to ejs) :

this.http.get(yourURL, {headers: this.headers, responseType: 'arraybuffer'})
      .subscribe( (result: any) => {
        let binary = '';
        const bytes = new Uint8Array( result );
        const len = bytes.byteLength;
        for (let i = 0; i < len; i++) {
          binary += String.fromCharCode( bytes[ i ] );
        }
        this.image = 'data:text/csv;base64,' + btoa(binary);
      });

With this solution, you can use the csv file in your front code, but it is not saved in the client's computer