Excel to JSON, dependency https://github.com/SheetJS/js-xlsx

xltojson.js

'use strict';

let XLSX = require('xlsx');
let workbook = XLSX.readFile(process.argv[3]);

let sheets = workbook.Workbook.Sheets.map(obj => obj.name);

let mails = sheets.reduce((acc, elem) => {
    let sheet = workbook.Sheets[elem];
    let mailArr = Object.keys(sheet).map(cell => sheet[cell].v).filter(val => val).filter((val, index) => index);
    return acc.concat(mailArr);
}, []);
console.log(JSON.stringify(mails, null, '\t'));