sum_of_1_n_numbers_rntm/index.js

Calculates the sum of 1-n numbers

module.exports = function sum(n) {
    try {
        const num = Number(n);

        if (num <= 0) throw "Number is smaller than 0.";

        return (num * (num - 1)) / 2;
    } catch (error) {
        throw error;
    }
}