Reduce list of 11 multiple (4) choice question answers to 4 character code, and re-inflate it again.

index.js

const CHARSET = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz$_';
const MASK = parseInt('111100', 2);

let guesses = [...Array(11)].map((item, index) => {
    return Math.floor(Math.random() * 4);
    // return index % 4;
});

console.log(guesses);

let remaining = guesses;
let triple;
let reducedTriple;
const reducedTriples = [];

while ((triple = remaining.slice(0,3)).length) {
    reducedTriples.push(triple.reduce((memo, guess, index) => {
         return memo + (guess << (index * 2));
    }, 0));

    remaining = remaining.slice(3);
}

const code = reducedTriples.map((num) => {
    return CHARSET.charAt(num);
}).join('');

console.log(code);

const inflatedGuesses = [];

code.split('').map((char) => {
    return CHARSET.indexOf(char);
}).forEach((reducedTriple) => {

    [...Array(3)].map((item, index) => {
        inflatedGuesses.push((reducedTriple >>> (index * 2)) & ~MASK);
    });

});

console.log(inflatedGuesses.slice(0, guesses.length));