csvparse.js

var csv = require('csv');
var fs = require('fs');

/* constants into csv */
const ARTIST_IDX = 0;
const SONG_IDX = 1;
const RECORD_IDX = 2;
const LABEL_IDX = 3;
const COUNT_IDX = 4; 


/* process the songs and store them in this arr */
let songs = [];
var songsLog = '';
var count = 0;

var parser = csv.parse({delimiter: ','}, function(err, data){
    count++;
    console.log(count);
    songs = [];
    songsLog = '';
    try {
        /* test if two rows in csv file are the same. */
        let match = function(a, b) {
            return a[ARTIST_IDX].trim().toLowerCase() == b[ARTIST_IDX].trim().toLowerCase()
                //&& a[SONG_IDX].trim().toLowerCase() == b[SONG_IDX].trim().toLowerCase()
                && a[RECORD_IDX].trim().toLowerCase() == b[RECORD_IDX].trim().toLowerCase();
        }

        /* iterate over all rows. for each entry, check if it matches any existing processed songs.
         * if so, increase the count variable. if not, set count variable to one and add it to
         * processed songs */
        
                data.forEach(entry => {
            let found = false;
            for (var i = 0; i < songs.length; i++) {
                if (match(songs[i], entry)) {
                    found = true;
                    songs[i][COUNT_IDX]++;
                }
            }
            if (!found) {
                entry.push(1); /* count idx */
                songs.push(entry)
            }
        });

        /* sort the array based on count idx */
        songs.sort((a, b) => {
            return b[COUNT_IDX] - a[COUNT_IDX];
        })

        /* top 50 only */
        songs = songs.slice(0, 50);



        /* string.format() from the internet */
        if (!String.prototype.format) {
          String.prototype.format = function() {
            var args = arguments;
            return this.replace(/{(\d+)}/g, function(match, number) {
              return typeof args[number] != 'undefined'
                ? args[number]
                : match
              ;
            });
          };
        }

        /* display it */ //send log back to server

        songs.forEach(song => {
            songsLog += "{0} - {1} by {2}. Album: {3} Label: {4}".format(song[COUNT_IDX], song[SONG_IDX], song[ARTIST_IDX], song[RECORD_IDX], song[LABEL_IDX]) + '<br>';
            //console.log("{0} - {1} by {2}. Album: {3} Label: {4}".format(song[COUNT_IDX], song[SONG_IDX], song[ARTIST_IDX], song[RECORD_IDX], song[LABEL_IDX]));

        })
    }
    catch(err) {
        console.log(err);
        songsLog = null;
     }
});

module.exports = function(filePath, cb) {
    //open a stream from the uploaded file
    var stream = fs.createReadStream(filePath);
    stream.pipe(parser);
    //when the stream is done, songsLog is complete and ready to be returned
    stream.on('close', function() {
        cb(songsLog);
    });
};