async csv To JSON data output in nodejs

Question

I have a terrible misunderstanding with promises in nodejs. I have a function in a module to convert CSV to JSON:

const URL_01 = `${__dirname}/URL/some_CSV.csv`;

const fs = require('fs'),
  Converter = require('csvtojson').Converter,
  converter = new Converter({}),

  convertToJson = function(file) {
    return new Promise( (res, rej) => {
      converter.on("end_parsed", (jsonData) => {
        if(!jsonData){
          rej("CSV to JSON conversion failed!")
        }
        res(jsonData);
      });
      fs.createReadStream(file).pipe(converter);
    });
  };

export default convertToJson;

Then I need to launch function convertToJson with CSVfile_URL in a server.js and save it to mongo db, now no data is output:

    app.get('/all', async (req, res) => {
  const data = await convertToJson( URL_01 );
  res.send(data);
});

Who could help me?

Cisco · Accepted Answer · 2018-03-03 04:11:55Z

3

Couple issues:

You're mixing ES2015 module syntax with CommonJS syntax which won't work.
Doesn't look like you're using csvjson correctly based on the documentation for the module here.

With that said, using this answer, something like this may work (untested):

const fs = require('fs')
const csv = require('csvtojson')

const URL_01 = `${__dirname}/URL/some_CSV.csv`;

module.exports = file => new Promise((resolve, reject) => {
  const promises = []
  csv()
    .fromFile(URL_01)
    .on('json', converted => promsies.push(Promise.resolve(converted)))
    .on('done', error => {
      if (error) {
        reject(error)
        return
      }
    Promise.all(promises).then(convertedResults => resolve(convertedResults))
  })
})

answered Mar 3, 2018 at 4:11

Cisco

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2 Comments

user2763557 Over a year ago

what if one is passing the file from client side to server? would i just put in the variable data inside fromFile?

Cisco Over a year ago

No. fromFile takes a path to the location of the file on disk. If you're trying to process a file from client side upload, I think .fromStream() would be better.

CyberT33N · Accepted Answer · 2021-10-25 21:59:00Z

const readStream = fs.createReadStream('yourFile.csv')

await new Promise((resolve, reject) => {
    csv(options)
        .fromStream(readStream)
        .subscribe(json=>{
            return new Promise((resolve, reject)=>{
                resolve(json)
            })
        })
        .on('header', header => {
            log(`Converting CSV to JSON - headers: ${headers}`)
        })
         .on('data', async data => {
                // data is a buffer object
                const jsonStr = data.toString('utf8')
                log(`Converting CSV to JSON - Current Line: ${jsonStr}`)
                await fs.appendFile(editDumb, jsonStr)
            })
        .on('done', () => {
            log('Finished converting CSV to JSON')
            resolve()
        })
        .on('error', e => {
            throw new BaseError(`Error while converting CSV to JSON - Error: ${e}`)
        })
})

user6269864 · Accepted Answer · 2018-07-03 09:39:19Z

-1

You may want to use a ready-made async-csv package from NPM. This will be as simple as:

const csv = require('async-csv');
let parsedObject = await csv.parse(csvFileAsString);

answered Jul 3, 2018 at 9:39

user6269864

1 Comment

Gibs Over a year ago

not working. I dont think async-csv can use await

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