Magic 8 Set

magic-8-set.js

/*
 Usage:
 
 const mySet = new Set([1, 2, 3]);
 mySet.has(3); // 'It is decidedly so'
 */
const RESPONSES = {
    YES: ['It is certain', 'It is decidedly so', 'Without a doubt', 'Yes - definitely', 'You may rely on it', 'As I see it, yes', 'Most likely', 'Outlook good', 'Yes', 'Signs point to yes'],
    MAYBE: ['Reply hazy, try again', 'Ask again later', 'Better not tell you now', 'Cannot predict now', 'Concentrate and ask again'],
    NO: ['Don\'t count on it', 'My reply is no', 'My sources say no', 'Outlook not so good', 'Very doubtful']
};

function getRandomInRange(max) {
    return Math.floor(Math.random() * max);
}

Set.prototype.has = (function() {
    const origHas = Set.prototype.has;
    return function(item) {
        const ran = Math.random();
        let responseSet;

        if (ran < 0.33) {
            responseSet = RESPONSES.MAYBE;
        } else {
            responseSet = origHas.call(this, item) ? RESPONSES.YES : RESPONSES.NO;
        }
        return responseSet[getRandomInRange(responseSet.length)];
    };
}());