CSVFile.js

import fs from 'fs';
import csv from '@fast-csv/format';

export class CSVFile {
    static write(filestream, rows, options) {
        return new Promise((res, rej) => {
            csv.writeToStream(filestream, rows, options)
                .on('error', err => rej(err))
                .on('finish', () => res());
        });
    }

    constructor(opts) {
        this.headers = opts.headers;
        this.path = opts.path;
        this.writeOpts = { headers: this.headers, includeEndRowDelimiter: true };
    }

    create(rows) {
        return CSVFile.write(fs.createWriteStream(this.path), rows, { ...this.writeOpts });
    }

    append(rows) {
        return CSVFile.write(fs.createWriteStream(this.path, { flags: 'a' }), rows, {
            ...this.writeOpts,
            // dont write the headers when appending
            writeHeaders: false,
        });
    }

    read() {
        return new Promise((res, rej) => {
            fs.readFile(this.path, (err, contents) => {
                if (err) {
                    return rej(err);
                }
                return res(contents);
            });
        });
    }
}