reverse-ASCII-art-mapper.js

// the generator singleton
const generatorSingleton = (() => {
    function getUniqueInstance() {
        if (!instance) {
            instance = this.getLetterRepresenations();
        }
        return instance;
    }
    let instance = null;
    return {getUniqueInstance};
})();

// art reverse-mapper
function getLetterFromArt(representation) {
    const generatorInstance = generatorSingleton.getUniqueInstance.bind(this)();
    return generatorInstance[representation] ? generatorInstance[representation] : '?';
}

// approximates the testing environment
function runTestingEnv() {

    // hidden function
    this.getLetterRepresenations = () => {
        console.log('G E N E R A T I N G   L E T T E R S...');
        const letters = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ';
        const representations = {};
        letters.split('')
            // reverse-mapped 'art' representation
            .map(letter => representations[letter + letter + letter] = letter);
        return representations;
    }

    console.log(getLetterFromArt.call(this, 'AAA'));        // G E N E R A T I N G   L E T T E R S...
                                                            // A
    console.log(getLetterFromArt.call(this, 'BBB'));        // B
    console.log(getLetterFromArt.call(this, 'XXX'));        // X
    console.log(getLetterFromArt.call(this, 'Who am I?'));  // ?
}

runTestingEnv();