Remove one csv from another and generate new csv

index.js

const fs = require('fs');
const parse = require('csv-parse');

const all = fs.readFileSync('./all.csv');
const confirm = fs.readFileSync('./confirm.csv');

parse(all, {}, (err, allMembers) => {
    parse(confirm, {}, (err, confirmedMembers) => {
        const confirmedMembersEmails = {};
        confirmedMembers.forEach(member => {
            confirmedMembersEmails[member[0]] = true;
        });
        const declineMembers = allMembers.filter((member) => {
            return !confirmedMembersEmails[member[0]];
        });

        declineMembers = allMembers.map(member => (member.splice(4)));
        var file = fs.createWriteStream('./decline.csv');
        declineMembers.forEach((v) => {
            file.write(v.join(',') + '\n');
        });
        file.end();
    });
});