fizzbuzz.js

const assert = require('assert');

function getFizzBuzzRules() {
    return [
        { label: ()  => 'fizzbuzz', rule: n => n % 15 === 0  },
        { label: ()  => 'buzz',     rule: n => n % 5  === 0  },
        { label: ()  => 'fizz',     rule: n => n % 3  === 0  },
        { label: (n) => n,          rule: n => n === n       },
    ];
}

function sequenceToFizzbuzz(sequence, separator = ', ') {
    return sequence.map(number => {
        const rule = getFizzBuzzRules().find(item => item.rule(number));
        return rule.label(number);
    }).join(separator);
}

describe('Fizzbuzz', function() {
    it('translate sequence 1, 2, 3, 4 and 5 to fizzbuzz', function() {
        assert.equal('1, 2, fizz, 4, buzz', sequenceToFizzbuzz([1, 2, 3, 4, 5]));
    });

    it('translate sequence 3, 5 and 15 to fizzbuzz', function() {
        assert.equal('fizz, buzz, fizzbuzz', sequenceToFizzbuzz([3, 5, 15]));
    });

    it('translate sequence 1, 2 and 3 to fizzbuzz', function() {
        assert.equal('1, 2, fizz', sequenceToFizzbuzz([1, 2, 3]));
    });
})