I am trying to create a function where I can pass file path and the read the file in async way. What I found out was that it supports streams()
const fs = require('fs'); var parse = require('csv-parse'); var async = require('async'); readCSVData = async (filePath): Promise<any> => { let csvString = ''; var parser = parse({delimiter: ','}, function (err, data) { async.eachSeries(data, function (line, callback) { csvString = csvString + line.join(',')+'\n'; console.log(csvString) // I can see this value getting populated }) }); fs.createReadStream(filePath).pipe(parser); } I got this code from here. but I am new to node js so I am not getting how to use await to get the data once all lines are parsed.
const csvData = await this.util.readCSVData(path) 2 Answers
My best workaround for this task is:
const csv = require('csvtojson') const csvFilePath = 'data.csv' const array = await csv().fromFile(csvFilePath); This answer provides legacy code that uses async library. Promise-based control flow with async doesn't need this library. Asynchronous processing with async.eachSeries doesn't serve a good purpose inside csv-parse callback because a callback waits for data to be filled with all collected data.
If reading all data into memory is not an issue, CSV stream can be converted to a promise:
const fs = require('fs'); const getStream = require('get-stream'); const parse = require('csv-parse'); readCSVData = async (filePath): Promise<any> => { const parseStream = parse({delimiter: ','}); const data = await getStream.array(fs.createReadStream(filePath).pipe(parseStream)); return data.map(line => line.join(',')).join('\n'); } 
