smart-column.js

'use strict';
let printf = require('printf');

let run = (sep, sheet) => {
    let recordFmt = col => '%-' + Math.max(...(sheet.map(line => line[col].length))) + 's';
    let fmt = sheet[0].map((e, i) => recordFmt(i)).join(sep);
    return sheet.map(line => printf(fmt, ...line)).join('\n');
}

let sheet = `to#titi#ta#tutu#a
toto#ti#tata#tu#b`.split('\n').map(e => e.split('#'));
console.log(run('#', sheet));