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');
}
