A more general FizzBuzz solution that also works for Raindrops

factor_converter.ts

type Factor = {
    n: number,
    word: string
};

function createConverter(factors: readonly Factor[]): (n: number) => string {
    return (n: number): string => {
        const converted = factors.map(f => n % f.n == 0 ? f.word : '').join('');
        return converted || `${n}`;
    };
}

const fizzbuzz = createConverter([
    {n: 3, word: 'Fizz'},
    {n: 5, word: 'Buzz'}
]);
[9, 35, 15, 8].forEach(n => console.log(fizzbuzz(n)));

const raindrops = createConverter([
    {n: 3, word: 'Pling'},
    {n: 5, word: 'Plang'},
    {n: 7, word: 'Plong'}
]);
[9, 10, 14, 15, 21, 35, 52, 105].forEach(n => console.log(raindrops(n)));